Split-aperture laser pulse compressor design tolerant to alignment and line-density differences

We introduce a four-pass laser pulse compressor design based on two grating apertures with two gratings per aperture that is tolerant to some alignment errors and, importantly, to grating-to-grating period variations. Each half-beam samples each grating in a diamond-shaped compressor that is symmetric about a central bisecting plane. For any given grating, the two half-beams impinge on opposite sides of its surface normal. It is shown that the two split beams have no pointing difference from paired gratings with different periods. Furthermore, no phase shift between half-beams is incurred as long as the planes containing a grating line and the surface normal for each grating of the pair are parallel. For grating pairs satisfying this condition, gratings surfaces need not be on the same plane, as changes in the gap between the two can compensate to bring the beams back in phase.     

Studies on the syntheses of polymetalloxanes and their properties as a precursor for amorphous oxide. VII. Preparation and properties of polyzirconoxanes as a precursor for zirconia fibers by the hydrolysis of bis (ethyl acetoacetato) zirconium dialkoxide

Acid-catalyzed hydolysis of bis(ethyl acetoacetato) zirconium dialkoxide in methanol or THF was investigated. The hydrolysis of the chelates in the molar ratios of H₂O/ chelate = 1.0–2.0 and HCl/chelate = 0.1–0.2 provided concentrated solutions (ca. 83 wt %) of polyzirconoxanes (PZO) which showed excellent spinnability and stability to self-condensation. Continuous gel fibers were prepared by dry spinning the solutions. Polyzirconoxanes were isolated as powders when the concentrated solution was precipitated with hexane. Silylation allowed the investigation of the structure of PZO. It was confirmed to be the polymers of a low degree of polymerization with the ligand and hydroxy group as pendants. © 1992 John Wiley & Sons, Inc.     

Ring and axis mode lasing in quasi-stadium laser diodes with concentric end mirrors

We fabricated quasi-stadium laser diodes whose resonators consist of two concentric curved end mirrors and two straight sidewall mirrors. We observed two lasing modes that correspond to different beam propagations along the cavity axis and along a ring trajectory, and different far-field patterns with wide angular separation. The modes can be selected by control of an electrode pattern. We also show that the far-field patterns numerically obtained by the extended Fox-Li mode calculation method are in good agreement with the experimental results.     

The separation of oligodeoxynucleotides having a single-base difference by affinity capillary electrophoresis using oligodeoxynucleotide- polyacrylamide conjugate

We have developed an affinity capillary electrophoresis for gene mutation assay. We show a method for separating a mixture of oligodeoxynucleotides having single-base difference using oligodeoxynucleotide-polyacrylamide conjugate. Because the conjugate behaved similarly to nonionic polyacrylamide in terms of migration rate, it can be used as a pseudoimmobilized affinity ligand in a polyacrylamide-coated capillary. Oligodeoxynucleotide having an oncogene sequence and a version with one base substituted were completely separated by this method. The magnesium-ion concentration was found to be a key factor in achieving efficient separation of oligodeoxynucleotides with the same chain length.     

Dipole excitation of alpha clusters in (6)Li and (7)Li

Dipole excitations in highly excited energy regions of (6)He and (7)He nuclei were investigated via the ((7)Li,(7)Be) reaction with an incident energy of 65A MeV at forward scattering angles. The resonances at Q approximately equal to -30 MeV observed commonly for both (6)Li and (7)Li targets were found to be excited via both spin-flip and spin-nonflip transitions with DeltaL = 1. Based on the observed excitation energy, width, and cross section of each resonance, the relevant resonances are inferred to be analogs of the dipole resonances of alpha clusters in the (6)Li and (7)Li nuclei.     

Reduction of Pt usage in fuel cell electrocatalysts with carbon nanotube electrodes

The 12 wt% Pt-deposited carbon nanotube electrode gives 10% higher voltages than 29 wt% Pt-deposited carbon black and reduces the Pt usage by 60% in polymer electrolyte fuel cells with hydrogen and oxygen.     

Synthesis of polyester by novel addition reaction of active di-ester with di-epoxy compound

Some polyesters having pendant ether groups were synthesized with high yield by polyaddition of active di-esters such as di(S-phenyl)thioisophthalate (PTIP) and di(S-phenyl)thiosebacate with di-epoxy compounds such as diglycidyl ether of bisphenol A (BPGE) and diglycidyl ether of ethylene glycol using some quaternary ammonium salts as a catalyst. The degree of polymerization in the reaction of PTIP with BPGE was strongly affected by the kind of reaction solvent, monomer concentration, the reaction temperature, and the kind of catalyst. As a result, it is found that tetrabutylammonium chloride has the highest catalytic activity for the polyaddition of PTIP with BPGE, and dimethylsulfoxide is a suitable solvent for the reaction system.     

5,5,15,15-Tetraoxo-5,15-Dithiaporphyrin as a Highly Electron-Deficient Porphyrinic Ligand

Oxidation of 5,15-dithiaporphyrin with meta-chloroperbenzoic acid afforded the corresponding S,S-tetraoxide in good yield. The resultant 5,5,15,15-tetraoxo-5,15-dithiaporphyrin exhibited the highly electron-deficient nature as elucidated by the electrochemical analysis and theoretical calculations. Treatment of tetraoxodithiaporphyrin with zinc(II) acetate and nickel(II) acetate provided the corresponding metal complexes efficiently. Owing to its enhanced Lewis acidity of the metal center by the electron-deficient ligand, the nickel complex underwent facile axial ligation to form pentacoordinate and hexacoordinate high-spin (S=1) complexes in solution and solid, respectively. The binding constant of pyridine to the Ni^II center was significantly higher than those of conventional porphyrin Ni^II complexes. Temperature-dependent magnetic susceptibility measurements of the high-spin Ni^II complex revealed the presence of weak ferromagnetic interactions.