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11.
AbstractTwo new alkaloids, fluevirines E (1) and F (2), along with six known Securinega alkaloids, were isolated from the methanol extract of the twigs and leaves of Flueggea virosa. The structures and absolute configurations of the new compounds were elucidated by means of MS, NMR, and ECD analyses. Compound 1 is a new dimeric indole alkaloid while 2 is a new securinega-type alkaloid. The in vitro cytotoxic activities of the isolated alkaloids against several human cancer cell lines and their acetylcholinesterase inhibitory activity were also evaluated. 相似文献
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本文首次提出一种可调实时时间差电子错位散斑干涉技术,并成功地用于热变形测量,该方法还可用于长时间连续变形和瞬态大变形的位移测量。叙述了该技术的原理,给出了一些应用的实验结果。 相似文献
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By the method of geometry of Banach spaces, we have proven that a bounded linear operator in Banach space is a compact linear one iff it can be uniformly approximated by a sequence of the finite rank bounded homogeneous operators, which reveals the essence of the counter example given by Enflo. 相似文献
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Laser sintering of a two-component metal powder layer on top of sintered layers, with a moving circular Gaussian laser beam is modeled numerically. The overlap between the adjacent scanning lines, as well as the binding between the newly sintered layer and existing sintered layers underneath through melting, are also considered. The governing equation is formulated by a temperature-transforming model, with partial shrinkage induced by melting taken into account. The liquid flow of the molten low melting point metal powders driving by capillary and gravity forces is formulated by Darcy’s law. The effects of the dominant processing parameters, including the moving laser beam intensity, scanning speed, and the number of the existing sintered layers underneath on the shape of the heat affected zone (HAZ) are investigated. PACS 44.05.+e; 81.20.Ev 相似文献
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A typical vascular model is established to study the effects of large blood vessels on the transient laser propagation during
optical imaging. A time-resolved Monte Carlo algorithm is developed to investigate transient light propagation in biological
tissues with embedded tumors and blood vessels. The results indicate that inclusion of the vasculatures could significantly
alter light propagation transients from those obtained from the tissue embedded with tumor only. 相似文献
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Let X,Y be Banach spaces and M a linear manifold in X×Y={{x,y}∣x∈X,y∈Y}. The central problem which motivates many of the concepts and results of this paper is the problem of characterization and construction of all extremal solutions of a linear inclusion y∈M(x). First of all, concept of metric operator parts and metric generalized inverses for linear manifolds are introduced and investigated, and then, characterizations of the set of all extremal or least extremal solutions in terms of metric operator parts and metric generalized inverses of linear manifolds are given by the methods of geometry of Banach spaces. The principal tool in this paper is the generalized orthogonal decomposition theorem in Banach spaces. 相似文献
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A new dual chemosensor (TTF-PBA) for Fe3+ and Cu2+ in different signal pathways was designed and synthesized. The absorption spectrum, fluorescence spectrum and cyclic voltammograms changed in the presence of Cu2+ and Fe3+. The optical color changed within 5 s from yellow to orange upon the addition of Cu2+, and it changed to dark yellow when Fe3+ existed. The cyclic voltammogram of Cu2+/TTF-PBA changed from Eox = 0.50 V, Ered = 0.32 V to Eox = 0.64 V, Ered = 0.80 V (vs Ag/AgCl) upon the addition of 2.0 equiv. Cu2+. As for Fe3+/TTF-PBA, its oxidation wave disappeared, and its reduction wave appeared at Ered = ?0.59 V (vs Ag/AgCl) upon the addition of 4.0 equv. Fe3+. The sensor displayed high selectivity for Cu2+ and Fe3+ over other ions including Pb2+, Zn2+, Ni2+, Ag+, Cr3+, Mn2+, Al3+, Co2+, Pd2+, Hg2+, Fe2+, Cd2+, Ce3+, Bi3+ and Au3+, the detection limits for Cu2+ and Fe3+ ion reached as low as 5.33 × 10?7 mol/L and 5.34 × 10?7 mol/L, respectively. Furthermore, when Fe3+ existed, Cu2+ can be detected sequentially by the sensor through the absorption spectrum and the color change observed by naked-eyes. 相似文献