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901.
Reaction of the [trans-B(20)H(18)](2-) ion with the n-butoxide ion, formed in situ from reaction of n-butanol and NaH, in tetrahydropyran (THP) produces in good yield an unexpected and isolable solvent-coordinated polyhedral borane anion, [ae-B(20)H(17)O(CH(2))(5)](3-). The anticipated product of nucleophilic attack, [ae-B(20)H(17)On-Bu](4-), is not observed under the reaction conditions. The solvent-coordinated product is also formed in the presence of either ethoxide or carbamate ion but is not observed if the ethoxide or carbamate ion is not present in stoichiometric amounts. In the presence of the n-butanethiol anion, the coordinated THP ring undergoes a ring-opening reaction, yielding the [ae-B(20)H(17)O(CH(2))(5)Sn-Bu](4-) anion. Ring opening is also observed in the presence of the ethoxide ion in refluxing THP. Isolation of the previously proposed analogous solvent-coordinated tetrahydrofuran (THF) product, [ae-B(20)H(17)O(CH(2))(4)](3-), was unsuccessful; however, the product resulting from ring opening of THF by the n-butanethiol anion is reported. 相似文献
902.
The use of metal organic frameworks (MOFs) for the catalytic production of nitric oxide (NO) is reported. In this account we demonstrate the use of Cu(3)(BTC)(2) as a catalyst for the generation of NO from the biologically occurring substrate, S-nitrosocysteine (CysNO). The MOF catalyst was evaluated as an NO generator by monitoring the evolution of NO in real time via chemiluminescence. The addition of 2, 10, and 15-fold excess CysNO to MOF-Cu(II) sites and cysteine (CysH) resulted in catalytic turnover of the active sites and nearly 100% theoretical yield of the NO product. Control experiments without the MOF present did not yield appreciable NO generation. In separate studies the MOF was found to be reusable over successive iterations of CysNO additions without loss of activity. Subsequently, the MOF catalyst was confirmed to remain structurally intact by pXRD and ATR-IR following reaction with CysNO and CysH. 相似文献
903.
Mandhan P Qi BQ Keenan JI Ismail S Beasley SW Sullivan MJ 《Journal of fluorescence》2006,16(5):655-658
Immunocytochemistry has emerged as a powerful research tool in neurobiology. One of the widely used methods is an indirect fluorescence technique that uses FITC- conjugated IgG to visualise protein expression within tissues, but a major drawback of this technique is the high background fluorescence due to non-specific antibody binding. Gut innervation is complex and best visualized in three-dimensions in whole mount preparations. We describe a simple and easy to use counterstaining procedure in conjunction with an indirect immunofluorescence technique in gut whole mount preparations that largely eliminates background fluorescence and creates a contrasting background against the bright antigen-antibody complexes. Furthermore, this technique allows the detailed qualitative and quantitative study of myenteric plexuses in whole-mount preparations. 相似文献
904.
A two-dimensional numerical simulation model for the elastodynamic wave propagation in two linear elastic, isotropic, joint half-spaces is presented. The border between the two half-spaced is graded in a way, that the values of the elastic properties and the densities vary smoothly (sinusoidally) from the values of one continuum to the values of the other continuum within a transition zone of a defined thickness. It is demonstrated, that a graded layer leads to a frequency and wavelength dependent refraction and reflection behavior of elastodynamic waves. Numerical results show that wavelengths which are long compared with the transition layer thickness are dominantly reflected whereas short waves are dominantly transmitted, a phenomena which does not occur in the case of an infinitely thin transition layer. Furthermore the frequency dependent reflection and transmission behavior of elastodynamic waves is verified experimentally. There the interface between two vapor deposited films is graded due to intermetallic diffusion effects. These graded microstructures are analyzed with a short-pulse-laser-acoustic set-up. The corresponding frequencies of the elastodynamic waves which are filtered with these functionally graded microstructures are in the range of 0.5 THz. 相似文献
905.
Schelter EJ Veauthier JM Thompson JD Scott BL John KD Morris DE Kiplinger JL 《Journal of the American Chemical Society》2006,128(7):2198-2199
Novel 4f-5f complexes of U(IV) and Th(IV) with Yb have been prepared using a terpyridyl-functionalized ketimide linking group. These 4f-5f heterotrimetallic complexes (C5Me5)2An[-N=C(CH2C6H5)(tpyYb(C5Me5)2)]2 (where An = Th, U) exist in Yb(II/III) valence equilibria and exhibit rich electrochemical behavior consistent with electronic coupling between the actinide and Yb(II/III)tpy*- moieties. The magnetic response of the uranium complex, studied qualitatively using a subtraction method, is indicative of a coupled magnetic state between the U(IV) and Yb(III)tpy*- groups at low temperatures. Both the electrochemical and magnetic data are in agreement and are consistent with differences in participation of the actinide valence orbitals in the ketimide bonding. 相似文献
906.
White RE Carlson CN Veauthier JM Simpson CK Thompson JD Scott BL Hanusa TP John KD 《Inorganic chemistry》2006,45(17):7004-7009
A series of new bulky allyl terpyridyl-ytterbium complexes have been synthesized to determine the effect of allyl ligands on the internal charge-transfer process that exists in these materials. Compared to the pentamethylcyclopentadienyl-ytterbocene compound Cp*2Yb(tpyCN) (nu(C(triple bond)N) = 2172 cm(-1)), the symmetrically substituted allyl complex [1,3-(SiMe3)2C3H3]2Yb(tpyCN) possesses a markedly lowered C(triple bond)N frequency of 2130 cm(-1). Furthermore, the electronic nature of these bulky allyl complexes can be tuned, as demonstrated by the C(triple bond)N frequency of the asymmetric derivatives [1-(SiMe3)C3H4]2Yb(tpyCN) and [1-(SiPh3)-3-(SiMe3)C3H3]2Yb(tpyCN) (2171 and 2164 cm(-1), respectively). The differences in these frequencies can be attributed to differences in the ligands' steric and electronic character. Single-crystal X-ray characterization of [1,3-(SiMe3)2C3H3]2Yb(tpy) reveals that the allyl moiety possesses shorter Yb-C and Yb-N bond distances than the Cp* analogue. The magnetic susceptibility data for [1,3-(SiMe3)2C3H3]2Yb(tpy) departs dramatically from the Curie law, with a room-temperature magnetic moment of 2.95 mu(B). 相似文献
907.
Assamoi Allah Antoine Destain Jacqueline Philippe Thonart 《Applied biochemistry and biotechnology》2010,160(1):50-62
There is an increasing interest for the organic residues from various sectors of agriculture and industries over the past
few decades. Their application in the field of fermentation technology has resulted in the production of bulk chemicals and
value-added products such as amino acid, enzymes, mushroom, organic acids, single-cell protein, biologically active secondary
metabolites, etc. (Ramachandran et al., Bioresource Technology 98:2000–2009, 2007). In this work, the production of extracellular xylanase by the fungus Penicillium canescens was investigated in solid-state fermentation using five agro-industrial substrates (soya oil cake, soya meal, wheat bran,
whole wheat bran, and pulp beet). The best substrate was the soya oil cake. In order to optimize the production, the most
effective cultivation conditions were investigated in Erlenmeyer flasks and in plastic bags with 5 and 100 g of soya oil cake,
respectively. The initial moisture content, initial pH, and temperature of the culture affected the xylanase synthesis. The
optimal fermentation medium was composed by soya oil cake crushed to 5 mm supplemented with 3% and 4% (w/w) of casein peptone and Na2HPO4.2H2O. After 7 days of incubation at 30 °C and under 80% of initial moisture, a xylanase production level of 18,895 ± 778 U/g
(Erlenmeyer flasks) and 9,300 ± 589 U/g (plastic bags) was reached. The partially purified enzyme recovered by ammonium sulfate
fractionation was completely stable at freezing and refrigeration temperatures up to 6 months and reasonably stable at room
temperature for more than 3 months. 相似文献
908.
为了快速准确进行西洋参和人参的品种鉴别,从主根横断面入手,采集其横断面的近红外光谱,分别从物理结构因素和化学因素方面对光谱进行了分析,选定特定波段进行物理因素主导建模、化学因素主导建模、理化因素综合建模,并对三种建模结果进行比较分析,发现三种模型判别率都在96%以上,都能很好的满足批量原材料快速检测的需求。物理因素模型运算简单,但判别率相对低。化学因素判别率较高,但运算量大。理化因素综合模型判别率最高为100%,无需预处理,运算量小,效果最理想,该结果说明近红外定性判别中物理结构因素有时也发挥重要作用。横断面鉴别法准确、便捷,可实际应用于企业原料药材的质量控制,实现对原料药材的快速筛查。 相似文献
909.
Albert Chawanda Cloud Nyamhere Francois D. Auret Jacqueline M. Nel Wilbert Mtangi Mmatsae Diale 《Physica B: Condensed Matter》2012,407(10):1570-1573
Ruthenium (Ru) Schottky contacts were fabricated on n-Ge (1 0 0) by electron beam deposition. Current–voltage (I–V), deep level transient spectroscopy (DLTS), and Laplace-DLTS techniques were used to characterise the as-deposited and annealed Ru/n-Ge (1 0 0) Schottky contacts. The variation of the electrical properties of the Ru samples annealed between 25 °C and 575 °C indicates the formation of two phases of ruthenium germanide. After Ru Schottky contacts fabrication, an electron trap at 0.38 eV below the conduction band with capture cross section of 1.0×10−14 cm−2 is the only detectable electron trap. The hole traps at 0.09, 0.15, 0.27 and 0.30 eV above the valence band with capture cross sections of 7.8×10−13 cm−2, 7.1×10−13 cm−2, 2.4×10−13 cm−2 and 6.2×10−13 cm−2, respectively, were observed in the as-deposited Ru Schottky contacts. The hole trap H(0.30) is the prominent single acceptor level of the E-centre, and H(0.09) is the third charge state of the E-centre. H(0.27) shows some reverse annealing and reaches a maximum concentration at 225 °C and anneals out after 350 °C. This trap is strongly believed to be V–Sb2 complex formed from the annealing of V–Sb defect centre. 相似文献
910.
Galbiati M Ferrier L Solnyshkov DD Tanese D Wertz E Amo A Abbarchi M Senellart P Sagnes I Lemaître A Galopin E Malpuech G Bloch J 《Physical review letters》2012,108(12):126403
We report on polariton condensation in photonic molecules formed by two coupled micropillars. We show that the condensation process is strongly affected by the interaction with the cloud of uncondensed excitons and thus strongly depends on the exact localization of these excitons within the molecule. Under symmetric excitation conditions, condensation is triggered on both binding and antibinding polariton states of the molecule. On the opposite, when the excitonic cloud is injected in one of the two pillars, condensation on a metastable state is observed and a total transfer of the condensate into one of the micropillars can be achieved. Our results highlight the crucial role played by relaxation kinetics in the condensation process. 相似文献