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71.
Simpson HJ Houston BH Liskey SW Frank PA Berdoz AR Kraus LA Frederickson CK Stanic S 《The Journal of the Acoustical Society of America》2003,114(3):1281-1290
Acoustic bottom penetration experiments were carried out in a medium-grain sandy bottom at a site in St. Andrews Bay, Florida. These investigations used a new buried, vertical, one-dimensional synthetic array system where a small hydrophone was water-jetted into the sediment to a depth of approximately 2 m. Once buried, this hydrophone was mounted to a vertical robotics stage that translated the hydrophone upward in 1-cm increments. A broadband (3 to 80 kHz) spherical source, positioned 50 cm above the sediment-water interface, was used to insonify the sediment. Measurements were made with insonification angles above and below the critical angle by changing the horizontal distance of the source relative to the insertion point. This new measurement system is detailed, and results are presented that include temporal, frequency, and wavenumber analysis for natural and roughened interfaces. The measured compressional sound speed and attenuation are shown to be self-consistent using the Kramers-Kronig relation. Furthermore, only a single fast compressional wave was observed. There was no observation of a second slower compressional wave as predicted by some applications of the Biot model to unconsolidated water-saturated porous media. 相似文献
72.
The first synthesis of a diacetylenic amide from Echinacea is reported. The key steps included the reaction of an aldehyde with the monoanion of a diacetylene and the reductive removal of a propargylic alcohol. 相似文献
73.
In so much as bis-macrocyclic peptidomimetics have been recognized as high affinity substrates for HIV-1 protease, we were interested in the design and synthesis of new bis-macrocyclic bioisosteric analogues whose general structure is displayed on Fig. 2. The structures of these new analogues are characterized by the specific replacement of the methylene of the benzyl group directly attached to the N-acyl glycine residue in the original molecule 1, by its main bioisosteres, i.e. O-, S- and NH-aryl groups. Knowing that an intermediate in which an heteroatomic aryl group is directly linked to a free amine glycine residue is not stable, we developed an original synthetic pathway which involved the coupling of a specific side chain to the exocyclic carboxylic acid function, followed by an elegant oxidation-nucleophilic substitution Steglich-type reaction. Analogues 2a-d were then submitted to chemical and enzymatic hydrolysis. We demonstrated that, as expected, the specific cleavage of the exocyclic N-acyl bond led to the release of aryl moieties (phenol, thiophenol and aniline species). These chemical and enzymatic stability studies brought to light the biological potential of such macrocyclic analogues in infected cells. 相似文献
74.
Jayasinghe UL Kumarihamy BM Bandara AG Waiblinger J Kraus W 《Natural product research》2003,17(1):5-8
Twenty nine solvent extracts from twenty Sri Lankan plants were examined for antifeedant activity against the fourth instar larvae of Mexican bean beetle, Epilachna varivestis Muls., Coccinellidae. Extracts of Sarcococca brevifolia (Buxaceae), Strychnus nux vomica (Loganiaceae), Diploclisia glaucescens, Coscinium fenestratum (Menispermaceae), Syzygium caryophyllatum (Myrtaceae), Pittosporium zeylanicum (Pittosporaceae), Lasianthus gardneri (Rubiaceae), Ferronia limonia (Rutaceae) and Allophylus cobbe (Sapindaceae) have shown strong antifeedant activity. 相似文献
75.
[reaction: see text] A synthetic approach to malibatol A featuring a novel benzofuran synthesis is described. 相似文献
76.
Let denote an elliptic curve over and the modular curve classifying the elliptic curves over such that the representations of in the 7-torsion points of and of are symplectically isomorphic. In case is given by a Weierstraß equation such that the invariant is a square, we exhibit here nontrivial points of . From this we deduce an infinite family of curves for which has at least four nontrivial points.
77.
78.
L. Kraus 《Czechoslovak Journal of Physics》1987,37(12):1348-1359
Magnetic anisotropy of rotationally symmetric samples is measured by a simple induction method based on transverse susceptibility measurements. The sample is magnetically saturated by a d.c. field perpendicular to the axis of rotation. A small a.c. field is applied in the direction perpendicular to both the d.c. field and the axis of rotation. The transverse a.c. susceptibility is measured by a Hartshorn bridge of mutual inductance. From the transverse susceptibilities along different directions the anisotropy constants as well as the saturation magnetization can be determined. 相似文献
79.
Daniela Kraus 《Journal of Mathematical Analysis and Applications》2008,345(2):628-631
The precise asymptotic behaviour of the solutions to the two-dimensional curvature equation Δu=k(z)e2u with e2u∈L1 for bounded nonnegative curvature functions −k(z) near isolated singularities is obtained. 相似文献
80.
L. Landois R. v. Jaksch J. B. Haycraft R. J. Williamson und F. Kraus 《Fresenius' Journal of Analytical Chemistry》1890,29(1):241-244
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