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51.
Internal friction techniques at 35 kHz were used to study the interactions between point defects and dislocations in crystals of silver chloride. The Granato-Lücke plots of the amplitude-dependent decrement were not linear, but were concave upward. Various analyses of these data all gave pin-dislocation binding energies of approximately 0·2 eV. An extensive study was made of the decay of the amplitude-independent decrement after “excitation” by high-amplitude oscillation; the Granato-Lücke L4 law was found valid, but the arrival of pins proceeded as t1/3, rather than the usual t2/3 found in deformed specimens. A first-order model of the response of a slightly perturbed Maxwell atmosphere about the dislocation is presented. The model quantitatively describes the experimental results. The activation energy of the rate constant was found to be 0·42 eV, consistent with data on solute diffusion and strain-aging. 相似文献
52.
A method is presented for the determination of americium and curium isotopes in environmental samples, an ion-exchange clean-up procedure being used. 相似文献
53.
Mukai C Kobayashi M Kubota S Takahashi Y Kitagaki S 《The Journal of organic chemistry》2004,69(6):2128-2136
A new procedure for constructing monocyclic five- and six-membered azacycles by the endo-mode ring-closing reaction of allenylazido derivatives under neutral conditions has been developed. The azabicyclo[m.n.0] compounds were prepared by applying this newly developed procedure. The seven-membered azacycle was prepared when the allene possessing an unsubstituted carboxyl amido functionality was submitted to the basic conditions. In addition, indole and quinoline skeletons were synthesized using this procedure. 相似文献
54.
Abe T Sato C Ushirogochi H Sato K Takasaki T Isoda T Mihira A Yamamura I Hayashi K Kumagai T Tamai S Shiro M Venkatesan AM Mansour TS 《The Journal of organic chemistry》2004,69(18):5850-5860
A novel and mild method was established to synthesize 6-methylidene penem compounds. This method entails a MgBr(2)/Et(3)N-promoted aldol-type condensation on 6-bromopenem 12 with an appropriately substituted aldehyde to yield the intermediate acetylated bromohydrin, which was smoothly converted to the final product with simultaneous deprotection of C3 carboxylic acid ester using activated zinc dust and phosphate buffer at pH 6.5. This process provides a useful variation of C-C bond formation method for penem derivatives and also serves as a practical synthetic method to prepare 6-exomethylenepenem derivatives without racemization at the C5 position. 相似文献
55.
Yasuaki Kawaguchi Shigeo Yasuda Akira Kaneko Yuki Oura Chisato Mukai 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(29):7738-7742
The efficient RhI‐catalyzed cycloisomerization of benzylallene‐alkynes produced the tricyclo[9.4.0.03,8]pentadecapentaene skeleton through a C H bond activation in good yields. A plausible reaction mechanism proceeds via oxidative addition of the acetylenic C H bond to RhI, an ene‐type cyclization to the vinylidenecarbene–RhI intermediate, and an electrophilic aromatic substitution with the vinylidenecarbene species. It was proposed based on deuteration and competition experiments. 相似文献
56.
57.
The Pauson-Khand reaction of enynes possessing a trimethylgermyl group at the alkyne terminus afforded the corresponding bicyclo[3.3.0]octenone and bicyclo[4.3.0]nonenone skeletons in a stereoselective manner. The resulting trimethylgermyl group of the bicyclic compounds was then converted to the iodo group, which was used for further elaboration. Thus, the trimethylgermyl group at the triple bond terminus was shown to be a precursor for other appendages. 相似文献
58.
59.
A method is proposed for measuring simultaneously several actinide elements by alpha-spectrometry. The actinides in sample solutions are sorbed together on an anion-exchange column from a nitric acid-methanol mixture. After simultaneous elution and electroplating on a disc, the actinides are determined by alpha-spectrometry. Radiochemical yields of the procedure for Th, U, Np, Pu, Am and Cm are better than 50%, all falling within a range of +/- 5%. Examples of the application of this method to various marine environmental samples such as sea-water, seaweed and marine sediment are presented. 相似文献
60.
Kaneda M Hyakuta K Takao Y Ishizuka H Fukai J 《Langmuir : the ACS journal of surfaces and colloids》2008,24(16):9102-9109
When a polymer solution droplet is deposited on a lyophobic surface, the contact line is moved back to some degree and subsequently pinned. An experimental setup is constructed to investigate not only the receding process but also an internal flow of polystyrene-acetophenone and -anisole solutions. As a result, the time variation of the evaporation rate per unit area during receding does not strongly depend on the initial solute concentration. The average solute concentration at the pinning of the contact line increases as the initial solute concentration increases. A convective circulation flow that is upward at the axis of symmetry is observed. This flow pattern is different from those of pure liquids such as water, acetone, benzene, and so forth, which have been previously reported. Furthermore, the observed flow is enhanced as the initial solute concentration increases, contrary to an increase in the fluid viscosity. To resolve these discrepancies, the mechanism of the flow is numerically investigated using a hemispherical droplet model considering the density and surface tension distributions. The numerical results demonstrate that the circulation flow that is experimentally observed is actually caused. It is also found that the solutal Rayleigh effect initially induces the internal flow, and subsequently the solutal Marangoni effect dominates the flow. Both effects are enhanced as the initial concentration increases because of the evaporative mass balance at the free surface. 相似文献