Gas permeation properties of blend and copolymer membranes composed of 1-trimethylsilyl-1-propyne and 1-phenyl-1-propyne structures

The poly(1-trimethylsilyl-1-propyne) (PMSP) has the potential to be an important membrane gas separation material due to the fact that it has the highest gas permeability of all polymeric membranes. One problem with PMSP is a decrease in the gas permeability with age. In order to understand the aging processes, we studied the change in free volume and the molecular motions of the PMSP and its membranes modified with 1-phenyl-1-propyne (PP) structures; that is, a copolymer and a blend of PMSP and PPP. During aging, the unrelaxed volume of the PMSP membrane was relaxed, and the molecular motion of carbons dropped, suggesting that the decrease in the microvoids caused a tighter chain packing. The copolymer and blend membrane had stable permeability compared to the PMSP. In particular, the addition of a small amount of the PP structure provided excellent stability with high gas permeability. A decrease in the unrelaxed volume of modified membranes was hardly observed with age; however, the molecular motion of some carbons slightly changed. This change did not affect the gas permeability. In this case, a larger unrelaxed volume was probably a dominant factor in the gas permeation of the PMSP rich membranes relative to the molecular motion in the T₁ measurement. © 1997 John Wiley & Sons, Inc.     

Fixation of Atmospheric Nitrogen: Synthesis of Heterocycles with Atmospheric Nitrogen as the Nitrogen Source

Dry air is the source of molecular nitrogen for reactions with TiL₄, Li, and TMSCl (L = Cl, OiPr; TMS = trimethylsilyl). The nitrogen–titanium complexes thus prepared can be used to synthesize indoles, pyrroles, and lactams from carbonyl compounds. Applying this method to 1 provides access to 2 , the key compound in the synthesis of (±)-lycopodine.     

Spectroscopic studies of charge-ordering system in organic conductors

Charge localization generates a non-uniform charge distribution in some organic conductors. Phase transitions accompanying such a localization of charge are studied by using infrared and Raman spectroscopy. We first introduce θ-(BEDT-TTF)₂MM′(SCN)₄ (M=Rb, Cs, Tl; M′=Zn, Co) as typical examples of a charge-ordering system, where BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene. We apply the same spectroscopic technique to α′-(BEDT-TTF)₂IBr₂, θ-(BDT-TTF)₂Cu(NCS)₂, and (TTM-TTP)I₃, which show the phase transitions from low-resistivity to high-resistivity state, where TTM-TTP is 2,5-bis[4,5-bis(methylsulfonyl)-1,3-dithiol-2-ylidene]-1,3,4,6-tetrathiapentalene.     

Measurement of Timing Jitter in Wavelength Tunable Femtosecond Soliton Pulses

We investigated the root mean square (RMS) timing jitter and RMS intensity noise of the wavelength tunable femtosecond soliton pulses using the technique of radio-frequency spectrum analysis. We obtained interesting results that the generated solitons have almost constant RMS timing jitter and RMS intensity noise of approximately 410 fs and 0.03% in the wavelength region of 1600-1750 nm. It is therefore believed that the magnitudes of the jitter and noise are not greatly increased in the process of wavelength tunable soliton pulse generation. The wavelength tunable soliton pulse is confirmed to be stable and useful for practical applications.     

EPC-K1 protects neuronal cells from peroxynitrite-mediated oxidative damage

Protective effects of EPC-K1 (L-ascorbic acid 2-[3,4-dihydro-2,5,7,8-tetramethyl-2-(4,8,12-trimethyldecyl)-2H-1-benzopyran-6-yl-hydrogen phosphate] potassium salt, a difunctional derivative of vitamin C and vitamin E) on neuronal cell damage mediated by peroxynitrite were studied. Primary cultures of cerebellar granule cells were exposed to peroxynitrite by treatment with 3-morpholinosydnonimine-N-ethylcarbamide (SIN-1), which generated nitric oxide and superoxide anion simultaneously upon decomposition. The results showed that SIN-1 treatment triggered time-dependent cell death, which was accompanied by the decrease in the cellular GSH level, the increase in the lipid peroxidation level, and the alteration of cell membrane biophysical characteristics. EPC-K1 showed only moderate scavenging effect on peroxynitrite, but could effectively protect neuronal cells from oxidative damage mediated by peroxynitrite.