Al等离子体类锂伴线的布居机制分析及实验应用

基于K壳层稳态碰撞辐射模型的程序,详细分析Al等离子体类锂伴线的主要布居机制,分别给出1s2p^{2 2}P-1s²2p²P,1s2s2p(¹S)²P-1s²2s²S与1s2p^{2 2}D-1s²2p² 关键词： 碰撞辐射模型 类锂伴线 线强比 激光等离子体     

Relation between soil matrix potential changes and water conversion ratios during methane hydrate formation processes in loess

With a new apparatus designed and assembled by ourselves, the matrix potential of non-saturated loess was firstly measured and studied during methane hydrate formation processes. The experimental results showed that during two formation processes, the matrix potential changes of the loess all presented a good linear relationship with water conversion ratios. In addition, although it was well known that the secondary gas hydrate formation was easier than the initial, our experimental results showed that the initial hydrate formation efficiency in non-saturated loess was higher than that of the secondary.     

Solid state photopolymerization of acrylic acid at low temperature

Near‐infrared spectroscopy was used to investigate the kinetic characteristics of acrylic acid photopolymerized at ?70°C and room temperature, respectively. The obtained results showed that at ?70°C the double bond conversion increased with increase in the initiator's concentration. Addition of soft chain component polyethylene glycol 400 (PEG400) could lead to high conversion in the solid state, and then high final double bond conversion after post‐curing. The introduction of water at low temperature also contributed largely to the enhancement in the initial and final double bond conversion in solid state. SEM photographs showed that more pores came up in the cured films with the increase in the water content in the reaction system. The change in the photoinitiator concentration, amount of PEG400, and content of water had significant effect on samples cured at lower temperature than at room temperature under the same conditions. Different kinds of photoinitiators showed different contributions to the initial and final double bond conversion on photopolymerization of acrylic acid at low temperature. Significant post‐curing phenomena for photopolymerization of acrylic acid at low temperature could be observed as well. Copyright © 2009 John Wiley & Sons, Ltd.     

Triterpenoids from the Flowers of Salvia miltiorrhiza

A phytochemical investigation of the flowers of Salvia miltiorrhiza Bunge led to the isolation of two new oleanane‐ and ursane‐type triterpenoids, (3α)‐olean‐12‐ene‐3,23‐diol ( 1 ) and (3α)‐urs‐12‐ene‐3,23‐diol ( 2 ), as well as of four known triterpenoids. Their structures were elucidated on the basis of spectroscopic evidence, including 1D‐ and 2D‐NMR, HR‐MS, and the X‐ray analysis, and by comparison with literature data.     

Effect of alkali-metal ions on the local structure and luminescence for double tungstate compounds AEu(WO4)2 (A = Li, Na, K)

The effect of alkali-metal ions on the local structure and luminescence properties for alkali-metal europium double tungstate compounds AEu(WO(4))(2) (A = Li, Na, K) has been investigated by a dual-space structural technique, atomic pair distribution function (PDF) analysis, and the Rietveld method of powder X-ray diffraction. The compounds AEu(WO(4))(2) (A = Li, Na) crystallize in the isostructure with the tetragonal space group I41/a (No. 88) and show the same luminescence properties in spite of the different doped alkali metals. However, KEu(WO(4))(2) crystallizes in monoclinic symmetry with the space group C2/c (No. 15). Compared with the two other counterparts, KEu(WO(4))(2) exhibits a more effective charge-transfer excitation, a larger Stokes shift, and a broader 612 nm emission band. This phenomenon is ascribed to the lower crystal symmetry in KEu(WO(4))(2), which influences bond distances and the coordination number of Eu(3+). Two complementary methods, the Rietveld method and PDF analysis, reveal that both LiEu(WO(4))(2) and NaEu(WO(4))(2) afford the same local surroundings of Eu(3+). The local structure determined by the Rietveld and PDF methods well account for the observed luminescent properties.     

Simultaneous detection of five antibiotics in milk by high-throughput suspension array technology

A new suspension array technology is proposed for the simultaneous quantitative determination of five antibiotics—tylosin, tetracycline, gentamicin, streptomycin, and chloramphenicol in milk. A novel treatment of milk samples for suspension array with diethyl ether was performed which greatly reduced the interference of the disturbing components in milk on the reaction results with no significant effect on detection sensitivity. Compared with using biotin labeled monoclonal antibody, using of secondary antibody-biotin make the detection sensitivity further improved. The minimum detectable concentration in samples of tylosin, tetracycline, gentamicin, streptomycin, and chloramphenicol were 0.3, 1.5, 4, 20, and 25 ng/ml, respectively, and the working ranges of samples were 6-400, 7-300, 8-200, 90-3000 and 70-8000 ng/ml, respectively. The mean recovery was 89.38-113.73% with a standard deviation within 16.62%. The suspension assay technology is powerful for the fast quantitative analysis of multi-antibiotics residue in milk.     

Synthesis of hept-6-en-2,4,5-triols and hept-6-en-2,3,5-triols

In a systematic effort to establish the relative as well as absolute configurations of two natural products isolated from Asomycete Daldinia concentrica, four independent (non-antipodal) diastereomers of hept-6-en-2,4,5-triol, the structure previously proposed for the natural products, were synthesized in enantiopure forms through a chiral-pool route and their optical rotation as well as NMR data were recorded. Although these four synthetic isomers cover all possible relative configurations the originally assigned triol may have, none of them gave spectroscopic data compatible with those reported for the natural products. Similar negative results were also obtained with a group of four non-antipodal diastereomers of hept-6-en-2,3,5-triol. The genuine structures of the natural products are therefore to be re-assigned.     

New dibenzocyclooctadiene lignans from the Kadsura ananosma

Fourteen new dibenzocyclooctadiene lignans, ananonins A-N (1-14), together with five known compounds, were isolated from the seeds of Kadsura ananosma. The structures and absolute configurations of 1-14 were established using a combination of MS, NMR, and CD techniques. The biological activity of these compounds was evaluated, and ananonin M (13) showed moderate neuroprotective effects in an in vitro assay.     

Bisleuconins A-D: a pair of epimeric ent-kauranoid dimers and two new asymmetric analogues isolated from Isodonleucophyllus

A phytochemical investigation of Isodon leucophyllus led to the isolation of four novel ent-kauranoid dimers: bisleuconins A-D (1-4), and one known compound, rabdoloxin A (5). It was interesting that the structures of bisleuconins A (1) and B (2) were elucidated as a pair of epimeric ent-kauranoid dimers with unique linkage pattern C-16→C-17′ to connect two monomers. Bisleuconins C (3) and D (4) were two new asymmetric ent-kauranoid dimers. A possible biogenetic pathway of 1 and 2 was also proposed.     

Electric-field response of discotic hexabenzocoronene (HBC) liquid crystals

A HBC derivative bearing six branched, space-demanding, alkyl side chains containing ether linkages has been synthesized and its thermotropic properties were investigated by polarization optical microscopy (POM) and differential scanning calorimetry (DSC). To our surprise, this molecule can respond to electric fields, and the influences of alternating current (AC) and directing current (DC) electric field on the assembly of this molecule in liquid crystal cells were discussed.