Numerical investigation of dynamical behavior of tethered rigid spheres in supersonic flow

The dynamical behavior of two tethered rigid spheres in a supersonic flow is numerically investigated. The tethered lengths and radius ratios of the two spheres are different. The two spheres, which are centroid axially aligned initially, are held stationary first, then released, and subsequently let fly freely in a supersonic flow. The mean qualities of the system and the qualities of the bigger sphere are considered and compared with the situations without the tether. In the separation process, six types of motion caused by the spheres, tether, and fluid interaction are found. The results show that the mean x-velocity of the system changes in a different manner for different radius ratios, and the x-velocity of the bigger sphere is uniformly reduced but through different mechanisms.     

系留气球电子设备防雷试验研究与应用

处于高空中的系留气球不可避免的存在着雷电与静电危害,会对测控系统位于球囊外的电子设备造成损坏,所以有必要对此类设备进行专门的防护,保证设备能安全工作。     

Synthesis, Characterization, and Luminescence Spectroscopic Accessibility Studies of tris(2,2′-Bipyridine)Ruthenium(II)-Labeled Inorganic-Organic Hybrid Polymers

The modified tris(2,2-bipyridine)ruthenium(II) complex 2 was anchored via a sol-gel process to different polysiloxane matrices to give a series of novel inorganic–organic hybrid polymers. One of the bipyridine ligands of 2 was provided with a long-chain spacer carrying a triethoxysilyl function (T group) at the end, which enables almost free mobility of the transition metal center. The polymers were swollen in several organic solvents of different polarity to investigate the luminescence behavior in the presence of quencher molecules. The luminescence of 2 was quenched using anthracene and atmospheric oxygen in appropriate concentrations of 5 · 10^–4 to 5 · 10^–3 and 3 · 10^–3 M, respectively. The luminescence behavior of 2 was determined by steady-state and time-resolved luminescence experiments. Translational mobilities of molecular species dissolved in the liquid phase were investigated by the kinetics of luminescence quenching after laser excitation. Both the translational mobility of anthracene and atmospheric oxygen, specified with the rate constant k₂ and the percentage of accessible luminescent centers were determined. Translational mobilities and the accessibility for anthracene and atmospheric oxygen in hybrid materials are significantly higher than in conventional Q type polysiloxanes.     

充气薄膜球囊测压法的数学方程

把流动坐标原点设在球囊中心,探讨了用充气薄膜球囊测量流体压力的数学方程,提出了应优选圆球囊测压,并分析了测压误差及误差处理方法,绘出了仿真曲线与实验曲线,通过实验验证了仿真的正确性.     

Single-molecule tethered particle motion to study protein-DNA interaction

Single-molecule techniques have been demonstrated as powerful tools to investigate individual protein-DNA interactions that are difficult to access by conventional biochemical techniques. These methods are popularly used to obtain valuable and detailed molecular mechanisms of enzyme functions. Currently, we have used single-molecule tethered particle motion to investigate protein-DNA interactions, including homologous recombination, site-specific recombination, DNA package, and the nucleosome remodeling process, and useful information was obtained. Here, we will describe the experimental designs and present the information obtained.     

Rhodium Indenyl NHC and Fluorenyl-Tethered NHC Half-Sandwich Complexes: Synthesis,Structures and Applications in the Catalytic C−H Borylation of Arenes and Alkanes

Indenyl (Ind) rhodium N-heterocyclic carbene (NHC) complexes [Rh(η⁵-Ind)(NHC)(L)] were synthesised for 1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazol-2-ylidene (SIPr) with L=C₂H₄ ( 1 ), CO ( 2 a ) and cyclooctene (COE; 3 ), for 1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene (SIMes) with L=CO ( 2 b ) and COE ( 4 ), and 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes) with L=CO ( 2 c ) and COE ( 5 ). Reaction of SIPr with [Rh(Cp*)(C₂H₄)₂] did not give the desired SIPr complex, thus demonstrating the “indenyl effect” in the synthesis of 1 . Oxidative addition of HSi(OEt)₃ to 3 proceeded under mild conditions to give the Rh silyl hydride complex [Rh(Ind){Si(OEt)₃}(H)(SIPr)] ( 6 ) with loss of COE. Tethered-fluorenyl NHC rhodium complexes [Rh{(η⁵-C₁₃H₈)C₂H₄N(C)C₂H_xNR}(L)] (x=4, R=Dipp, L=C₂H₄: 11 ; L=COE: 12 ; L=CO: 13 ; R=Mes, L=COE: 14 ; L=CO: 15 ; x=2, R=Me, L=COE: 16 ; L=CO: 17 ) were synthesised in low yields (5–31 %) in comparison to good yields for the monodentate complexes (49–79 %). Compounds 3 and 1 , which contain labile alkene ligands, were successful catalysts for the catalytic borylation of benzene with B₂pin₂ (Bpin=pinacolboronate, 97 and 93 % PhBpin respectively with 5 mol % catalyst, 24 h, 80 °C), with SIPr giving a more active catalyst than SIMes or IMes. Fluorenyl-tethered NHC complexes were much less active as borylation catalysts, and the carbonyl complexes were inactive. The borylation of toluene, biphenyl, anisole and diphenyl ether proceeded to give meta substitutions as the major product, with smaller amounts of para substitution and almost no ortho product. The borylation of octane and decane with B₂pin₂ at 120 and 140 °C, respectively, was monitored by ¹¹B NMR spectroscopy, which showed high conversions into octyl and decylBpin over 4–7 days, thus demonstrating catalysed sp³ C−H borylation with new piano stool rhodium indenyl complexes. Irradiation of the monodentate complexes with 400 or 420 nm light confirmed the ready dissociation of C₂H₄ and COE ligands, whereas CO complexes were inert. Evidence for C−H bond activation in the alkyl groups of the NHC ligands was obtained.     

Two remarkable epimerizations imperative for the success of an asymmetric total synthesis of (+)-aigialospirol

Two remarkable epimerization processes were uncovered during our pursuit of an enantioselective synthesis of(+)-aigialospirol featuring a cyclic acetal tethered ring-closing metathesis.Through modeling,we were able to turn these two unexpected epimerizations to our advantage via modeling to ensure a successful and concise total synthesis,thereby firmly establishing cyclic acetal tethered RCM as a powerful strategy in natural product synthesis.Most importantly,calculations allowed us to fully understand the ...     

Solid-supported biomimetic membranes with tailored lipopolymer tethers

Stable lipid membranes with controlled substrate-membrane spacing can be prepared using well-defined lipopolymers as a tether. Based on the living cationic ring-opening polymerization of 2-methyl- or 2-ethyl-2-oxazoline, lipopolymers can be synthesized bearing a lipid head group as well as a silanol reactive coupling end group. Using a “grafting onto” procedure these polymers can form dense, brush like monolayers, whose layered structures can be obtained by x-ray reflectivity measurements. By transfer of a pre-organized monolayer that is followed by vesicle fusion, stable polymer supported lipid membranes can be prepared. The substrate-membrane spacing can be controlled via the degree of polymerization, while the lateral diffusion of lipids within the membrane depends on the density of polymer tethers. Preliminary experiments implied that the membrane with long (N = 40) polymer tethers could reside trans-membrane receptors homogeneously, suggesting a large potential of this strategy.     

系留缆绳的应用特点与发展趋势

随着系留气球平台的发展和应用,作为空中设备与地面设施的唯一连接纽带——系留缆绳,其重要性开始被人们所关注,对其安全性与可靠性的要求也越来越高。结合系留缆绳的应用需求,讨论了系留缆绳的技术特点,并对其未来的发展趋势进行了分析。     

系留缆绳的设计概述

系留缆绳是系留气球浮空器系统的关键部件,直接关系到系统运行的安全性与可靠性等。介绍了系留缆绳的分类与结构。根据其使用要求与特点,归纳了系留缆绳的设计原则,并在此基础上提出了系留缆绳的设计方法以及注意事项。