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171.
172.
Numerical simulations with a monotonicity preserving flow solver have been performed to study shock diffraction phenomena and shock wave generated vorticity. The computations were performed using the conservative Finite Element Method-Flux Corrected Transport (FEM-FCT) scheme, which has been shown to have an excellent predictive capability for various compressible flows with both strong and weak shocks. An adaptive unstructured methodology based on adapting to high density and entropy gradients was used in conjunction with a conservative shock-capturing scheme to adequately resolve strong and weak flowfield gradients. The chief interest was the formation of vorticity arising from shock wave propagation over a sharp corner and the high accuracy and resolution of the interacting compressible wave features. Numerical simulations were compared with previous experimental results and exhibited remarkably good agreement in terms of compressible wave propagation, as well as vorticity development and transport. The computations also allowed insight into the fundamental fluid dynamics, specifically shock diffraction, vortex convection and shock-vortex interactions. 相似文献
173.
Supramolecular chemistry has been employed to develop flexible and adaptable multivalent neoglycoconjugates for binding galectin-1 (Gal-1). Gal-1, a dimeric lectin with two galactoside-binding sites, regulates cancer progression and immune responses. Self-assembled pseudopolyrotaxanes consisting of lactoside-displaying cyclodextrin (LCD) "beads" threaded onto polyviologen "strings" display mobile ligands as a result of cyclodextrin rotation about, and limited translation along, the polymer chain. The pseudopolyrotaxanes rapidly and efficiently precipitate Gal-1 and provide valency-corrected enhancements of up to 30-fold compared to native lactose and 20-fold over free LCD in a T-cell agglutination assay. A supramolecular statistical effect was observed, wherein the efficacy of Gal-1 inhibition correlates with the number of ligands connected to each other solely through mechanical and noncovalent interactions. Such flexible and adaptable self-assembled pseudopolyrotaxanes show promise for the study of multivalent interactions and targeting of therapeutically relevant lectins. 相似文献
174.
Investigations of Sb–Sb Bond Formation Reactions in the Coordination Sphere of Transition Metals The reaction of SbCl3 with various transition metal metalates of the type K[MLn] [MLn = Ni(CO)Cp*, Fe(CO)Cp′, Co(CO)4; Cp* = η5‐C5Me5, Cp′ = η5‐C5H4Me] in the presence of [Cr(CO)5thf] have been studied. With K[Ni(CO)Cp*] and K[Fe(CO)2Cp′] the trigonal‐pyramidal complexes [(μ3‐Sb){Ni(CO)Cp*}3] ( 1 ) and [(μ3‐Sb){Fe · (CO)2Cp′}3] ( 2 ), respectively, are obtained. The reaction with K[Co(CO)4] leads to the tetrahedral cluster [Co3(CO)9(μ3‐Sb{Cr(CO)5})] ( 3 ) and the butterfly cluster [Co2(CO)6(μ‐SbCl)(μ‐SbCl{Cr(CO)5})] ( 4 ). All products are characterised by X‐ray crystal structure determination. In contrast to the corresponding [(CO)5CrPCl3] system forming P–P bonds, starting from SbCl3/[Cr(CO)5thf] does not cause a Sb–Sb bond formation. 相似文献
175.
Lithium-silylindolide as Precursor of 1,2-, 1,3-Bis(silyl)indoles and Bis(indole-1,3-yl)silane Lithium-indolide reacts with difluorosilanes (F2SiR2: R = CHMe2 ( 1 ); CMe3 ( 2 )) in a molar ratio 2 : 1 with formation of bis(indole-1-yl)silanes. The 1-(di-tert-butylfluorosilyl)-3-(fluorodiisopropylsilyl)indole ( 3 ) is obtained in the reaction 1-(di-tert-butylfluorosilyl)-3-lithium-indolide and F2Si(CHMe2)2. In a molar ratio 2 : 1 the bis(1-di-tert-butylfluorosilyl-indole-3-yl)diisopropylsilane 4 is formed. As a byproduct bis(1-di-tert-butylfluorosilyl-indole-3-yl)dimethylmethane ( 5 ) is isolated. A cleavage of THF and the formation of (indole-1-yl)diisopropylvinyloxysilan ( 6 ) occurs in the reaction of 1-diisopropylfluorosilylindole with t-BuLi in THF. 1-(di-tert-butylfluorosilyl)indole reacts with n-BuLi/TMEDA accompanied by an 1,2-anionic silyl group migration to give the 2-(di-tert-butylfluorosilyl)-1-lithiumindolide 7 . Hydrolysis of 7 gives the 2-(di-tert-butylfluorosilyl)indole ( 8 ). In the reaction of 7 with F2Si(CHMe2)2 the 1-(diisopropylfluorosilyl)-2-(di-tert-butylfluorosilyl)indole 9 is obtained. 1-n-Butyl-diisopropylsilylindole ( 10 ) is the product of the reaction of F2Si(CHMe2)2, n-BuLi/TMEDA and indole at –70 °C. Lithium-indolide reacts with 3 to give the 1-(di-tert-butylfluorosilyl)indole-3-yl)(indole-1-yl)-diisopropylsilane ( 11 ), the first example of this class of substances. In the reaction of 1 , F2SiMe2, and t-BuLi in THF the 1-(diisopropyl(indole-1-yl)silyl)-3-dimethyl-(3.3-dimethylbutylsilyl)indole 12 is isolated. The crystal structures of 2 , 5 and 9 are discussed. 相似文献
176.
Andreas Purath Carsten Dohmeier Elke Baum Ralf Kppe Hansgeorg Schnckel 《无机化学与普通化学杂志》1999,625(12):2144-2148
Molecular Compounds containing SiAl4, SiAl3, and GeAl4 Units: Sythesis and Structure of Si(AlCl2 · OEt2)4, Ge(AlCl2 · OEt2)4, and HSi(Cp*AlBr)3 In the scope of our investigations of the reactivity and the potential for synthesis of solutions of AlI halides we performed reactions between these solutions and SiCp or GeCp, respectively. From these reactions we could isolate an unusual cluster with a central Al14Si unit, described elsewhere, and the compounds Si(AlCl2 · OEt2)4, Ge(AlCl2 · OEt2)4, and HSi(Cp*AlBr)3, which will be presented and discussed here. In these species the Si respectively the Ge atoms are connected to 4 respectively 3 Al atoms. This bonding results in strong negative polarized Si/Ge centres. The change of the polarization with respect to “normal” Si–R or Ge–R linking leads to a drastic weakening of the Si–R respectively the Ge–R bonds. 相似文献
177.
178.
Christoph Üffing Elke Baum Ralf Kppe Hansgeorg Schnckel 《Angewandte Chemie (International ed. in English)》1998,37(17):2397-2400
A first indication of the reaction mechanism for the disproportionation of an AlI species to an AlIII compound and metallic aluminum is provided by the isolation of [Cp*3Al5I6], an intermediate that is formed in the ready disproportionation of [Cp*Al] in the presence of Al2I6 (see reaction sequence). This potentially key role of AlI compounds could be of great significance for large-scale industrial processes. X=I, Cl. 相似文献
179.
Yanyao Jiang Walter Ott Christian Baum Michael Vormwald Horst Nowack 《International Journal of Plasticity》2009
An event independent cumulative damage (EVICD) fatigue prediction model was previously developed for the fatigue damage prediction under general multiaxial stress state and loading conditions. The model takes the plastic strain energy as the major contributor to the fatigue damage. The application of the EVICD model does not require a cycle counting method for general random loading. In the current effort, derivations were made to explicitly and directly relate the material constants in the fatigue model to the parameters in the Manson–Coffin equations and the cyclic stress–strain curve of the material. In addition, an advanced cyclic plasticity theory was implemented for the determination of the detailed stress–strain response that was required as the input for the EVICD fatigue model. Three metallic materials were used to demonstrate the capability of the modified fatigue model for the predictions of fatigue lives under different loading conditions. The results show that the fatigue model can provide fatigue life predictions in close agreement with the experimental observations. 相似文献
180.
In the present study, a CMOS high speed camera system was employed for two-dimensional thermographic phosphor thermometry.
By the pixelwise evaluation of the luminescence lifetimes, a temperature map of a phosphor layer can be obtained. Using spatially
and temporally isothermal conditions in a tube furnace, a temperature lifetime characteristic was determined for the phosphor
Mg4FGeO6: Mn and was compared with data obtained by point measurements using a photomultiplier tube. Both, the pixel-to-pixel and
the shot-to-shot standard deviation were evaluated at different temperatures. Non-linearities and pixel-to-pixel inhomogeneities
of the CMOS chip were characterised and corrected employing a homogeneous light source. 相似文献