用于二聚物三能级蒸气激光系统的环形谐振腔设计

针对二聚物三能级蒸气激光系统增益相对于泵浦光方向显著的不对称特性,本文设计了一种稳定的能够充分利用介质增益特性的环形谐振腔,给出了象散和慧差补偿及泵浦激光与谐振腔匹配的条件。文中还给出了Na_2B~1Ⅱ_u-X~1∑_g~+跃迁激光谐振腔设计数据。     

The thermolysis of dicarbonylcyclopentadienyliron dimer: The formation of biferrocene

The thermolysis of dicarbonylcyclopentadienyliron dimer in a sealed tube at 300°C has been reported to produce ferrocene, carbon monoxide, carbon dioxide, cyclopentadiene and elemental iron. We observe in addition to these products the production of biferrocene and elemental carbon. Thermolysis of carbonylcyclopentadienyliron tetramer (produced from the dimer by thermolysis in refluxing xylene) produces ferrocene, iron and carbon monoxidre; no biferrocene, carbon dioxide or elemental carbon are produced. A scheme is proposed to account for these products.     

Fracture mechanisms of Hg0.8Cd0.2Te induced by pulsed TEA-CO2 laser

The fracture mechanisms of Hg_0.8Cd_0.2Te induced by pulsed TEA-CO₂ laser have been investigated theoretically and experimentally in this paper. The Hg_0.8Cd_0.2Te target was irradiated by a TEA-CO₂ laser with wavelength of 10.6 μm and spike width of 240 ns in an ambient atmosphere. The evident cracks can be found on the surface of the target from the scanning electron microscopy (SEM) photos, indicating that the severe breaks happened during the experiment. Theoretical analysis has also been carried out and the results show that the fracture of Hg_0.8Cd_0.2Te is mainly induced by thermal stresses, although there are three forces (thermal stress, evaporation wave and laser-supported detonation (LSD) wave) exerted on the target surface during the process.     

Preparation of a cyclodextrin dimer linked with a bis(picolinyl)cystine moiety and its intra- and intermolecular inclusion behavior

A novel cyclodextrin (CD) dimer linked with a bis(picolinyl)cystine (Cys) moiety was prepared by the coupling of Boc-protected Cys with amino-modified CDs, followed by deprotection of the Boc groups and bispicolinylation. The dimer showed less affinity to an organic guest molecule compared to that of a native CD monomer. It was attributed to an intramolecular inclusion of the pyridine moiety into CD cavity. The dimer caused significant increase of its organic guest affinity by an addition of a copper ion. The included pyridine group may come out of a CD cavity to bind the copper ion and the two CDs included cooperatively and intermolecularly a guest molecule with high affinity.     

A Novel Asymmetric ent-Kauranoid Dimer from Isodon enanderianus

ＩｎｔｒｏｄｕｃｔｉｏｎＩｓｏｄｏｎｅｎａｎｄｅｒｉａｎｕｓ (Ｈａｎｄ . Ｍａｚｚ .)Ｈ .Ｗ .Ｌｉ(Ｌａｂｉａｔａｅ) ,ｗｉｄｅｌｙｄｉｓｔｒｉｂｕｔｅｄｉｎｔｈｅｓｏｕｔｈｅｒｎｐａｒｔｓｏｆＹｕｎｎａｎＰｒｏｖｉｎｃｅ ,ｈａｓｂｅｅｎｕｓｅｄｉｎＣｈｉｎｅｓｅｔｒａｄｉｔｉｏｎａｌｆｏｌｋｍｅｄｉｃｉｎｅａｓａｎｔｉ ｉｎｆｌａｍｍａｔｏｒｙａｎｄｄｅｔｏｘｉｆｉｅｄａｇｅｎｔ.1Ｐｒｅｖｉｏｕｓｐｈｙｔｏｃｈｅｍｉｃａｌｉｎｖｅｓｔｉｇａｔｉｏｎｈａｓｓｈｏｗｎｔｈｅｐｒｅｓ ｅｎｃｅｏｆａｓｅｒ…     

A Large Conformational Change of a Bridged β-Cyclodextrin Dimer in Aqueous Solution

A novel bridged β-CD dimer in which two β-cyclodextrins were linked by a naphthalene at positions 2 and 7 has been synthesized. 1H and 13CNMR measurements showed that a large change in the conformation of the dimer occurred in aqueous solution. The dimer interacted with methyl and ethyl orange to form stable inclusion complexes via "induced fit" mechanism.     

Intramolecular dimers: a new design strategy for fluorescence-quenched probes

Fluorogenic probes dual-labeled with reporter and quencher dyes use a change in fluorescence to monitor biochemical events (e.g., substrate binding or enzyme digestion). Such events change the reporter-quencher distance, which affects fluorescence. Recently, it is has been shown that static quenching through intramolecular dimers is an important mechanism that can sometimes be more efficient than F?rster resonance energy transfer (FRET).     

Chemical composition of “AKD vapour” and its implication to AKD vapour sizing

Alkyl ketene dimer (AKD) sizing of paper involves the redistribution of the wax over the fibre surface upon heating. The two major mechanisms widely studied so far are the spreading of an autophobic precursor of molten AKD and AKD vapour transport and re-deposition on the fibre surface. All previous work assumed that the transport of AKD vapour could be expressed by the change of water contact angle with substrates that were exposed to the vapour. Information regarding the chemical composition of the vapour phase above the AKD wax has not been found in the literature. In this work, a simple method for analysing the chemical composition of the vapour is established. Our preliminary results indicated that the chemical composition of AKD vapour in the temperature range of 75–80 °C is dominantly fatty acids. This suggests that the sizing effect by actual AKD molecules via the vapour deposition mechanism is likely to be insignificant in this temperature range. This also implies that fatty acids play a positive role in AKD sizing. The chemical stability of AKD in this temperature range is also studied.     

Synthesis and X-ray structural study of octa-coordinated hexafluoroacetylacetone hafnium(IV) complex

Hexafluoroacetylacetonate hafnium(IV) complex has been synthesized and studied by X-ray structural analysis. Crystal data for C₃₀H₈F₃₆Hf₂O₁₄ are: a = 12.957(3) Å, b = 16.687(3) Å, c = 12.398(3) Å, β = 108.97°, space group P2₁/c, Z = 2, d _calc = 2.137 g/cm³, R = 0.047. The molecular structure is built from discrete binuclear molecules of Hf₂(OH)₂(hfac)₆ composition; the Hf...Hf distance in dimer is 3.533 Å. The structural units are connected by van der Waals interactions in the crystal.     

Crystal structure of oxotitanium(IV) 2,2,6,6-tetramethyl-3,5-heptanedionate

The structure of titanyl dipivalylmethanate TiO(dpm)₂ has been studied by X-ray diffraction analysis. The compound has a molecular structure formed by isolated centrosymmetrical dimers [TiO(dpm)₂]₂; the unit cell contains two structurally related, crystallographically unique binuclear molecules. The Ti...Ti distance in the dimer is 2.73 Å. Crystal data for Ti₂C₃₆H₇₆O₁₀: a = 32.477(6) Å, b = 14.409(3) Å, c = 25.630(5) Å; β = 107.82(3)°, space group C2/c, Z = 8, d _calc = 1.002 g/cm³.