Synthesis of light-harvesting dendrimers focally anchored with crown ethers or terpyridine ligands

Crown ethers and terpyridine ligands have been successfully attached to the focal point of light harvesting phenylacetylene monodendrons through Pd-catalyzed coupling reactions. The structures of these functional monodendrons were characterized by 1H and 13C NMR spectroscopy, mass spectrometry and elemental analysis. Such binding-ligand anchored dendrons exhibit broad absorption, large molar extenction coefficients and high fluoresence quantum yields. Coordination of crown ethers with alkali ions results in a significant increase in absorption strength in the UV range, but little alteration in either intensity or position of fluorescence emission. Coordination of terpyridine ligands with Ru2+, however, does efficiently quench the fluorescence from the dendrons,albeit only the smallest dendron exhibits efficient binding.     

VEGF regulates haematopoietic stem cell survival by an internal autocrine loop mechanism

Vascular endothelial growth factor (VEGF) is a principal regulator of blood vessel formation and haematopoiesis, but the mechanisms by which VEGF differentially regulates these processes have been elusive. Here we describe a regulatory loop by which VEGF controls survival of haematopoietic stem cells (HSCs). We observed a reduction in survival, colony formation and in vivo repopulation rates of HSCs after ablation of the VEGF gene in mice. Intracellularly acting small-molecule inhibitors of VEGF receptor (VEGFR) tyrosine kinase dramatically reduced colony formation of HSCs, thus mimicking deletion of the VEGF gene. However, blocking VEGF by administering a soluble VEGFR-1, which acts extracellularly, induced only minor effects. These findings support the involvement in HSC survival of a VEGF-dependent internal autocrine loop mechanism (that is, the mechanism is resistant to inhibitors that fail to penetrate the intracellular compartment). Not only ligands selective for VEGF and VEGFR-2 but also VEGFR-1 agonists rescued survival and repopulation of VEGF-deficient HSCs, revealing a function for VEGFR-1 signalling during haematopoiesis.     

钢铁企业产成品物流控制中转库流向的优化问题

以我国大型钢铁企业上海宝山钢铁集团(公司)为背景,描述了其产成品物流控制中的产成品转库问题,建立了转库流向优化问题的数学规划模型·使用遗传算法,提出一种称为“两段式可重复非负整数编码”的编码策略来获得大规模01规划模型的近优解·计算结果表明,当可用能力足够大并且准发数较少时,结果与SAS/OR的计算结果非常接近·当可用能力不是足够大,并且准发数较多时,计算结果要好于实际调度结果,此时SAS/OR软件在规定的时间内无法算出优化解·     

Configuration assignments of yrare high-spin structures in 126Cs

High-spin states in ¹²⁶Cs were populated in the reaction ¹¹⁶Cd(¹⁴N, 4n) at a beam energy of 65 MeV. About 50 new transitions were placed in a level scheme that consists of six rotational structures, three of which have been observed for the first time. The newly observed bands and a previously reported but uninterpreted band were assigned configurations based on their population, aligned angular momentum, energy signature splitting and B(M1)/B(E2) ratios (for the strongly coupled bands).Received: 16 September 2002, Revised: 10 March 2003, Published online: 1 July 2003PACS: 21.10.Re Collective levels - 27.60.+j      

Structure of Degenerate Block Algebras

Given a non-trivial torsion-free abelian group (A,+,Q), a field F of characteristic 0, and a non-degenerate bi-additive skew-symmetric map : A A F, we define a Lie algebra = (A, ) over F with basis {e_x | x A/{0}} and Lie product [e_x,e_y] = (x,y)e_x+y. We show that is endowed uniquely with a non-degenerate symmetric invariant bilinear form and the derivation algebra Der of is a complete Lie algebra. We describe the double extension D( , T) of by T, where T is spanned by the locally finite derivations of , and determine the second cohomology group H²(D( , T),F) using anti-derivations related to the form on D( , T). Finally, we compute the second Leibniz cohomology groups HL²( , F) and HL²(D( , T), F).2000 Mathematics Subject Classification: 17B05, 17B30This work was supported by the NNSF of China (19971044), the Doctoral Programme Foundation of Institution of Higher Education (97005511), and the Foundation of Jiangsu Educational Committee.     

Real time monitoring of nucleic acids ligation based on molecular beacon

The replication, ligation and repair of nucleic acids are essential life processes that based the survival, pro-creation and evolution of creatures. These interactions involving proteins (enzymes) and nucleic acids have fas-cinated great interest of scientists[1]. The nucleic acids ligation has been revealed that it is catalyzed by ligase and co-enzyme (ATP or NAD)[2—4]. Along with in-depth re-search, the nucleic acids ligation becomes a significant and common tool employed in bioengineerin…     

Bidirectional, synchronously pumped, ring optical parametric oscillator

We report the operation of a bidirectional femtosecond pulsed ring optical parametric oscillator based on periodically poled lithium niobate, pumped alternately with nonsimultaneous pulses from a Ti:sapphire mode-locked laser. A beat note between the two counterpropagating beams attests to a gyro response without dead band. The sensitivity of the device to differential phase changes is demonstrated by measurement of the nonlinear index of lithium niobate.     

High-conversion-efficiency, diode-pumped continuous-wave Raman laser

We demonstrate a diode-pumped cw Raman laser in H(2) with photon-conversion efficiency of (66+/-8)%. Pumped by an injection-locked diode laser at 792 nm, the Stokes laser produces a peak output power of ~16mW at 1180 nm. Accompanying the high Stokes power are deviations from the existing theory, which are believed to be caused by the thermal-lensing effect of the Raman gas.     

Fullerene-sensitized

[reaction: see text] Fullerene catalyzes the cycloaddition of dimethyliminodiacetate to maleimides under photolysis to form 2,5-dimethoxycarbonylpyrrolidine derivatives.