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M. Rosenberger D. Andrews F. DiMaria A. J. Duggan G. Saucy 《Helvetica chimica acta》1972,55(1):249-255
A novel and general synthesis of δ-lactones from glutaraldehyde is described. The dialdehyde is first reacted with an alkyl or substituted alkyl Grignard reagent to afford a δ-hydroxyaldehyde in good yield. These aldehydes exist preferentially in the cyclic hemiacetal form (δ-lactols). Oxidation of the latter compounds to give δ-lactones is readily achieved with silver oxide or bromine. The δ-lactols and δ-lactones serve as intermediates for the total synthesis of steroids. 相似文献
4.
Meroquinene (1), a key degradation product of quinine and an important intermediate in the preparation of the cinchona and other alkaloids,1 has only recently been synthesized 2 even though attempts were made at its preparation for over thirty years. These early attempts were frustrated primarily by the difficulty encountered in the introduction of a potential vinyl group onto a piperidine ring. Alkylation of 3-car-bethoxy-N-benzoyl-4-piperidone (2) with either phenoxyethyl chloride3 or dimethylaminoethyl chloride (3)4 resulted in exclusive formation of the O-alkylated product, even though alkylation of the presumably analogous 2-carbethoxycyclohexanone with 3 gave nearly equal amounts of C- and O- alkylated materials.4 The use of other piperidone derivatives in this reaction was precluded by the report that attempts to alkylate 3-car-bethoxy-N-alkyl-4-piperidones gave only the quaternary nitrogen product.5 相似文献
5.
Michael F. Duggan 《Experimental Mechanics》1980,20(7):233-239
The slotted-tension shear test provides an accurate method of measuring the inplane shear response of fiber-reinforced composite materials. Data from the slotted-tension test is compared with rail, ±45-deg tension, modified lap-shear and off-axis shear tests. It is shown that reinforced materials of any combination of fibers and fiber orientation can be tested using the new shear-testing technique. 相似文献
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Chaoying Wan Feng Zhao Xujin Bao Bala Kandasubramanian Matt Duggan 《Journal of Polymer Science.Polymer Physics》2009,47(2):121-129
Polyamide 12/Trisilanolphenyl‐POSS (PA 12/POSS) composites were prepared via melt‐compounding. The effect of polyhedral oligomeric silsesquioxane (POSS) on crystalline structure and crystalline transition of PA 12 was investigated by wide‐angle X‐ray diffraction (WAXD) and real time fourier transform infrared spectroscopy (FTIR). WAXD results indicated that PA 12 crystallized into γ‐form as slowly cooling from melt and the presence of POSS did not influence the crystalline structure of PA 12. Both PA 12 and PA 12/POSS composites underwent Brill transitions when they were heated from room temperature to melt point. Real time FTIR patterns showed that an absorption band at 697 cm?1 ascribed to Amide V (α) mode was emerged along with the disappearance of Amide VI (γ) band at 628 cm?1 with the increase of the temperature for PA 12 and PA 12/POSS composites, which suggested that the γ‐form crystalline has transformed into α form. The Brill bands were identified and the transformed mechanism was discussed based on the real FTIR results. The addition of POSS enhanced the tensile strength and thermal stability of PA 12. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 121–129, 2009 相似文献
9.
We analyze an infinitely repeated version of the Downsian model of elections. The folk theorem suggests that a wide range
of policy paths can be supported by subgame perfect equilibria when parties and voters are sufficiently patient. We go beyond
this result by imposing several suitable refinements and by giving separate weak conditions on the patience of voters and
the patience of parties under which every policy path can be supported. On the other hand, we show that only majority undominated
policy paths can be supported in equilibrium for arbitrarily low voter discount factors: if the core is empty, the generic
case in multiple dimensions, then voter impatience leads us back to the problem of non-existence of equilibrium. We extend
this result to give conditions under which core equivalence holds for a non-trivial range of voter and party discount factors,
providing a game-theoretic version of the Median Voter Theorem in a model of repeated Downsian elections.
J. Duggan was supported by the National Science Foundation, grant number 0213738, is gratefully acknowledged. 相似文献
10.
The Feynman path integral Monte Carlo approach has been coupled to the gauge including atomic orbital formalism in order to analyse the absolute magnetic shieldings of the benzene nuclei under the conditions of thermal equilibrium. The Hamiltonian employed in the derivation of ensemble averaged NMR quantities is of the Hartree-Fock type. The basis set used is of 6–31G quality. The spatial delocalization of the atoms leads to a deshielding of both types of benzene nuclei relative to the shieldings experienced at the minimum of the potential energy surface. This deshielding has to be traced back to bond length elongations in thermal equilibrium. The influence of the nuclear fluctuations on the NMR parameters of benzene is quantum driven up to temperatures of 400 K; classical fluctuations are of minor importance in this low-temperature window. 相似文献