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Ogawa AK DeMattei JA Scarlato GR Tellew JE Chong LS Armstrong RW 《The Journal of organic chemistry》1996,61(18):6153-6161
We report our synthesis of the C(26)-C(37) fragment of serine/threonine protein phosphatase PP1 and PP2A inhibitor calyculin C (1). Outlined in this paper are synthetic approaches to the two components based on disconnection at the C(33)-N(3) amide bond. We report the successful synthesis of the C(33)-C(37) aza-sugar derived from D-lyxose which was coupled onto a C(26)-C(32) aminooxazole originating from L-pyroglutamic acid. Elaboration of the resulting amide to a fully deprotected C(26)-C(37) fragment of calyculin C completed our synthesis. This provided an appropriate phosphonium salt for use in a Wittig olefination for joining both halves of the natural product. 相似文献
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We consider diffraction by a semi-infinite crack located alonga fusion interface between two differing elastic media. Twotypes of crack, namely open and partially closed cracks, areinvestigated. An open crack is modelled by a stress-free contactboundary condition and a partially closed crack is modelledby a spring contact boundary condition. For the latter, thejump in the stress across the crack is assumed to be proportionalto the jump in the displacement across the crack. This situationarises in, for example, a K-weld where the fine grain of theparent material (for example, ferritic or forged austeniticsteel) is in stark contrast with the coarse-grained weld metal(for example, austenitic weld metal). In the metal weld thedirection of the grain axis varies through the metal. However,diffraction is a local phenomenon and so the austenitic steelis assumed to have a zonal axis so that it may be modelled bya transversely isotropic composite. The ferritic or forged austeniticsteel will be modelled as an isotropic material. 相似文献
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Silvio Mollo Gianluca Iezzi Guido Ventura Andrea Cavallo Piergiorgio Scarlato 《Journal of Non》2012,358(12-13):1624-1628
Pt-capsules loaded with a Pt-coil and two crystalline seeds immersed into an andesitic melt were rapidly cooled from 1300 to 1100 °C with a rate of 3 °C/min at atmospheric pressure and air oxygen fugacity. Results show that the Pt-coil does not induce any heterogeneous crystallization process as well as iron diffusion process from the melt into the platinum substrate. In contrast, the presence of crystalline seeds in a solidifying andesitic melt significantly alters the phase assemblage, composition and texture of the new-forming crystals in response to a heterogeneous nucleation mechanism and the formation of metastable phases. 相似文献
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Compliance and enforcement in fisheries are important issues from an economic point of view since management measures are useless without a certain level of enforcement. These conclusions come from the well‐established theoretical literature on compliance and enforcement problems within fisheries and a common result is that, it is efficient to set fines as high as possible and monitoring as low as possible, when fines are costless and offenders are risk neutral. However, this result is sensitive to the assumption that fishermen cannot engage in avoidance activities, e.g., activities to reduce the likelihood of being detected when noncomplying. The paper presents a model of fisheries that allows the fishermen to engage in avoidance activities. The conclusions from the model are that, under certain circumstances, fines are costly transfers to society since they not only have a direct positive effect on the level of deterrence, but also an indirect negative effect in the form of increased avoidance activities to reduce the probability of detection. The paper contributes to the literature on avoidance activities by introducing the externality from the illegal behavior as an endogenous effect on other offenders. For an externality, that has an exogenous effect on other actors, Malik shows that fines are only costly transfers for conditional deterrence (when one actor is deterred while another actor is not). For fisheries, we show that fines are also costly transfers under no deterrence (when no agents are deterred). 相似文献
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Zambelli B Bellucci M Danielli A Scarlato V Ciurli S 《Chemical communications (Cambridge, England)》2007,(35):3649-3651
The binding constants between Ni2+ and Helicobacterpylori NikR have been determined using isothermal titration microcalorimetry in order to rationalize the role of this protein as a nickel-dependent biological sensor. 相似文献
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We show that a sequence of polynomials can be eigenfunctionsof a second-order differential operator only under severe restrictions. 相似文献
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Boron is available in the form of metal borates, especially of sodium and calcium, in nature[1]. The production of boron compounds has substantially increased recently due to increasing uses of these compounds in nuclear technology, in rocket engines as f… 相似文献