The 4051-Angstroms band of C3 (A 1Piu-X 1Sigmag +, 000-000): perturbed low-J lines and lifetime measurements

Rotational analyses have been carried out at high resolution for the 000-000 and 000-100 bands of the A (1)Pi(u)-X (1)Sigma(g) (+) transition of supersonic jet-cooled C(3). Two different spectra have been recorded for each band, using time gatings of 20-150 and 800-2300 ns. At the shorter time delay the spectra show only the lines observed by many previous workers. At the longer time delay many extra lines appear, some of which have been observed previously by [McCall et al.Chem. Phys. Lett. 374, 583 (2003)] in cavity ring-down spectra of jet-cooled C(3). Detailed analysis of these extra lines shows that at least two long-lived states perturb the A (1)Pi(u), 000 state. One of these appears to be a (3)Sigma(u) (-) vibronic state, which may possibly be a high vibrational level of the b (3)Pi(g) state, and the other appears to be a P = 1 state with a low rotational constant B. Our spectra also confirm the reassignment by McCall et al. of the R(0) line of the 000-000 band, which is consistent with the spectra recorded towards a number of stars that indicate the presence of C(3) in the interstellar medium. Fluorescence lifetimes have been measured for a number of upper-state rotational levels. The rotational levels of the A (1)Pi(u) state have lifetimes in the range of 230-190 ns, decreasing slightly with J; the levels of the perturbing states have much longer lifetimes, with some of them showing biexponential decays. An improved value has been obtained for the nu(1) vibrational frequency of the ground state, nu(1) = 1224.4933 +/- 0.0029 cm(-1).     

Intramolecular Diels-Alder Reactions of Thio-Substituted Dienes with Enones

Thio-substituted dienes bearing an enone moiety were readily prepared from 3-sulfolenes, and their intramolecular Diels-Alder (IMDA) reactions were studied. Octahydronaphthalenones were produced in good yield with high stereoselectivity. Hexahydroindenones were also obtained, but the stereoselectivity was lower.     

A validated HPLC method with ultraviolet detection for the determination of buformin in plasma

A sensitive and rapid high-performance liquid chromatographic assay is developed and validated for the determination of buformin in plasma. After addition of metformin as the internal standard, the analytes were deproteinated with acetonitrile, washed with dichloromethane, and the resulting supernatant injected. Chromatography was performed at ambient temperature by pumping a mobile phase of 0.03 m diammonium hydrogen phosphate buffer (pH 7, 250 mL) in methanol (750 mL) at a fl ow rate of 1 mL/min through a silica column. Buformin and metformin were detected at 236 nm, and eluted 9.8 and 15.4 min, respectively. No endogenous substances were found to interfere. Calibration curves were linear over the concentration range of 20-2000 ng/mL. The limit of quantitation was 20 ng/mL. The intra- and inter-day relative standard deviation (RSD) was 8.3%, or less, and the accuracy was within 10.1% of the relative error (RE). The method is suitable in pharmacokinetic investigation of buformin.     

Two-frequency two-photon ionization of nascent PO(X2II) from the collision-free IR photolysis of dimethyl methylphosphonate

We report the detection of nascent PO produced via the collision-free IR photolysis of dimethyl methylphosphonate. Absorption throughout the B²Σ⁺ ← X²Π system is followed by excitation using 266 nm radiation, which results in PO⁺ + e. Spectral features due to spin-orbit excitation appear extremely “cold” relative to vibrations and rotations.     

青蒿素及其一类物结构和合成的研究——Ⅸ.全合成青蒿素中若干关键化合物的合成

青蒿素是一个含有过氧基团的新型倍半萜内酯~([1]),它具有突出的抗疟作用~([2])。本文报道     

Synthesis of 4-[(1,3-diaminopyrrolo[3′,4′:4,5]pyrido[2,3-d]-pyrimidin-8-yl)benzoyl]-L-glutamic acid as a potential antifolate

This paper is dedicated to the memory of Professor Roland K. Robins The synthesis of 4-[(1,3-diaminopyrrolo[3′,4′:4,5]pyrido[2,3-d]pyrimidin-8-yl)benzoyl]-L-glutamic acid ( 18 ), a potential antifolate and anticancer agent, has been achieved starting from 1,4-dibromobutan-2-ol with alkyl p-aminobenzoic acids. Condensation of these two agents gave 1-(4-alkoxycarbonylphenyl)pyrrolidin-3-ols 7a,b , which were oxidized to the corresponding pyrrolidin-3-one derivatives 8a,b . Compounds 8a,b were converted into 1,3-diamino-8-(4-alkoxycarbonylphenyl)-7,8-dihydro-9H-pyrrolo[3′,4′:4,5]pyrido[2,3-d]pyrimidines 12a,b in 4 steps. Saponification of 12b the benzoate ester and coupling with di-tert-butyl glutamate afforded a mixture of 7,8-dihydro product 16 and its aromatized derivative 17 . Finally hydrolysis of esters 16 or 17 gave only the title compound 18 . The 7,8-dihydro tricyclic derivatives were easily air-oxidized to form their fully aromatized compounds. The title compound 18 was one tenth less active than MTX against HL-60 cells in culture.     

三辛基氧化膦(TOPO)萃取铟的研究

本文研究了三辛基氧化膦(TOPO)自盐酸溶液中萃取铟的性能,其萃取率是随酸度的增加而增加。与P_(350)和TBP相比较,萃取能力大小顺序为:TOPO>P_(350)>TBP经斜率法和化学分析法研究确定,TOPO白盐酸溶液中萃取铟的反应为:In_((a))~(3+)+H_((a))~++4Cl_((a))~-+2TOPO_((o))F(?)HInCl_4·2TOPO_((o))IR和NMR研究证明:铟是以H[InCl_4]形式被萃入TOPO有机相中的。     

Effect of take-up speed on physical properties and permeation performance of cellulose acetate hollow fibers

Cellulose acetate (CA) ultrafiltration hollow fibers were spun via the dry-jet wet spinning technique. The effect of the take-up speed on the mechanical properties, morphology, thermal properties, pure water permeation, retention, and surface characterization of hollow fiber membranes were investigated. Both the inner and outer diameters of the hollow fiber decreased with the increase of take-up speed. Macrovoids were observed on the inner surface of the drawn hollow fibers. The d-space decreased with the increase of the take-up speed. The ultimate tensile stress (UTS) increased and the breaking elongation decreased with the increase of take-up speed. The permeation performance was measured. The hydraulic permeability increased and the retention decreased slightly with the increase of the take-up speed. The surface roughness increased with the increase of the take-up speed. The thermal analysis results showed that the endothermic peak shifts to the higher temperature region and coefficient of thermal expansion (CTE) decrease for a higher take-up speed.     

Syntheses and PE-Spectroscopic Investigations of 2,6- and 3,5-Bridged 1,4-Dimethylidenecyclohexanes

Three 1,4-dimethylidenecyclohexanes, bridged in the 2,6- and 3,5-positions by two ethano ( 4 ), one ethano and one propano ( 5 ), and two propano bridges ( 6 ) have been synthesized. The interaction of the two exocyclic methylidene groups has been investigated by He(I) photoelectron (PE) spectroscopy. It revealed a slightly larger energy difference (0.8 eV) for 4 and 5 as compared to the parent 1,4-dimethylidenecyclohexane ( 7 ) (0.7 eV). The interpretation of the PE spectra was based on the comparison with PE data of related systems and with the results of semiempirical calculations on 4–6 .     

Ternary upper-critical-solution-temperature behavior in a blend system comprising poly(2,6-dimethyl-1,4-phenylene oxide), poly(4-methyl styrene), and polystyrene

 Upper-critical-solution-temperature (UCST) behavior in a ternary blend of poly(2,6-dimethyl-1,4-phenylene oxide), poly(4-methyl styrene), and polystyrene is reported. The as-cast ternary blend is immiscible at ambient conditions and comprises two different phases, and, however, turns into a miscible system above the “clarity point” ranging from 160 to 300 °C for different ternary compositions. The maximum clarity point is labeled as the UCST for the ternary system, which is about 295 °C. Above the clarity point, the originally immiscible ternary blend turned into one miscible phase. Owing to the thermodynamic UCST behavior and kinetic hindrance, the immiscible ternary polymer blend can be locked into a pseudo-miscible state if it is heated to a temperature above the clarity point followed by a rapid-cooling processing scheme. The quenched ternary blend can remain in a pseudo-miscible state as long as the service temperature does not exceed the glass-transition temperature of the blend. Received: 17 July 2001 Accepted: 3 October 2001