Angle-resolved photoemission study of the MX-chain compound [Ni(chxn)(2)Br]Br(2): spin-charge separation in hybridized d-p chains

We report on the results of angle-resolved photoemission experiments on a quasi-one-dimensional (1D) MX-chain compound [Ni(chxn)2Br]Br2, which shows a gigantic nonlinear optical effect. A "band" having about 500 meV energy dispersion is found in the first half of the Brillouin zone, but disappears at kb/pi approximately 1/2. These spectral features are well reproduced by the d-p chain model with a small charge-transfer energy Delta compared with that of 1D Cu-O compounds. We propose that this smaller Delta is the origin of the absence of clear spin-charge separation in the photoemission spectra and the strong nonlinear optical effect.     

Novel [D-Arg2]dermorphin(1-4) analogs with mu-opioid receptor antagonist activity

Ten Tyr-D-Arg-Phe-betaAla-NH(2) (YRFB) analogs in which specific amino acid side chains are shifted to the N(alpha)-position were synthesized, and the binding to these analogs to the mu receptor and their in vitro biological properties were evaluated. Some analogs in which a N,N-bis(p-hydroxybenzyl)-Gly residue was substituted for Tyr(1) exhibited mu receptor antagonist activities (pA(2)) between 5.3 and 6.1. Of these analogs, [N,N-bis(p-hydroxybenzyl)-Gly(1)]YRFB was found to be the most potent specific antagonist for the mu-opioid receptor.     

Photon-Counting Phase-Modulation Fluorometer

We propose a phase-modulation fluorometer that is applicable to a very weak fluorescence intensity level. In order to counter the single-photon event situation, we have introduced a combination of a time-to-amplitude converter and a pulse height analyzer (PHA) to the fluorometer, the combination of which is usually used in the single-photon correlation method to measure fluorescence decay waveforms with pulsed excitation. In the proposed fluorometer, a sinusoidal response waveform that is shifted in phase over the reference one is obtained statistically as a histogram in the PHA memory, and then the fluorescence lifetime can be calculated by the same procedure as the conventional analog phase-modulation method. The excitation light source used was a current-modulated ultraviolet light-emitting diode, whose center wavelength was 370 nm and whose spectral bandwidth was 10 nm. Fluorescence lifetimes of 17.5 ns and 5.7 ns obtained for 10 ppb quinine sulfate in 0.1 N H₂SO₄ and for 10 ppb rhodamine 6G in ethanol, respectively, agreed well with those reported in the literature. In passing, we report that the fluorescence lifetime of benzo[a]pyrene in dichloromethane is 14.6 ns, which is known as one of the carcinogenic, environmental-pollution materials.This paper was originally presented at the 2001 International Conference (2nd Joint OSJ-SPIE Conference) on Optical Engineering for Sensing and Nanotechnology, ICOSN 2001 which was held June 6#x2013;8, 2001 at the Pacifico-Yokohama Conference Center, Yokohama, Japan.     

Sub-ppm laser spectroscopy of antiprotonic helium and a CPT-violation limit on the antiprotonic charge and mass

Six laser-resonant transitions have been detected in metastable antiprotonic helium atoms produced at the CERN Antiproton Decelerator. They include UV transitions from the last metastable states in the v = n-l-1 = 0 and 1 cascades. Zero-density frequencies were obtained from measured pressure shifts with fractional precisions between 1.3 x 10(-7) and 1.6 x 10(-6). By comparing these with QED calculations and the antiproton cyclotron frequency, we deduce that the antiproton and proton charges and masses agree to within 6 x 10(-8) with a confidence level of 90%.     

Facile synthesis of functionalized 4-aminopyridines

The title compounds are readily available by ring transformation of nitropyrimidione with active methylene compounds in the presence of ammonium acetate.     

A new cyclopentanone annulation of α-bromomethylacrylates

Direct couplings of the α-bromomethylacrylates and the doubly charged succinate ion are described.