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1.
A new 20-membered macrolide designated exiguolide has been isolated from the marine sponge Geodia exigua, and its structure determined by interpretation of spectroscopic data. Exiguolide specifically inhibited fertilization of sea urchin (Hemicentrotus pulcherrimus) gametes but not embryogenesis of the fertilized egg. 相似文献
2.
Jet-cooled high-resolution infrared spectra of partially deuterated hydronium ion (HD2O+) in the O-H stretch region (nu3 band) are obtained for the first time, exploiting the high ion densities, long absorption path lengths, and concentration modulation capabilities of the slit-jet discharge spectrometer. Least-squares analysis with a Watson asymmetric top Hamiltonian yields rovibrational constants and provides high level tests of ab initio molecular structure predictions. Transitions out of both the lower (nu3(+)<--0(+)) and the upper (nu3(-)<--0(-)) tunneling levels, as well as transitions across the tunneling gap (nu3(-)<--0(+)) are observed. The nu3(-)<--0(+) transitions in HD2O+ acquire oscillator strength by loss of D(3h) symmetry, and permit both ground-state-[27.0318(72) cm(-1)] and excited-state-[17.7612(54) cm(-1)]-tunneling splittings to be determined to spectroscopic precision from a single rovibrational band. The splittings and band origins calculated with recent high level ab initio six-dimensional potential surface predictions for H3O+ and isotopomers [X. C. Huang, S. Carter, and J. M. Bowman, J. Chem. Phys. 118, 5431 (2003); T. Rajamaki, A. Miani, and L. Halonen, J. Chem. Phys. 118, 10929 (2003)] are in very good agreement with the current experimental results. 相似文献
3.
Melissa M. Cadelis Soeren Geese Benedict B. Uy Daniel R. Mulholland Shara J. van de Pas Alex Grey Bevan S. Weir Brent R. Copp Siouxsie Wiles 《Molecules (Basel, Switzerland)》2021,26(4)
Antimicrobial bioassay-guided fractionation of the endophytic fungi Neofusicoccum australe led to the isolation of a new unsymmetrical naphthoquinone dimer, neofusnaphthoquinone B (1), along with four known natural products (2–5). Structure elucidation was conducted by nuclear magnetic resonance (NMR) spectroscopic methods, and the antimicrobial activity of all the natural products was investigated, revealing 1 to be moderately active towards methicillin-resistant Staphylococcus aureus (MRSA) with a minimum inhibitory concentration (MIC) of 16 µg/mL. 相似文献
4.
In this paper, we obtain a recursive dimension formula for all γ- graded Lie algebras 𝔏 = +α∈γ𝔩α with finite dimensional homogeneous sub-spaces, where T is a countable abelian semigroup satisfying a certain finiteness condition. We apply this dimension formula to several Lie algebras to obtain explicit and simple dimension formulas. 相似文献
5.
Many advances in organic photovoltaic efficiency are not yet fully understood and new insight into structure‐property relationships is required to push this technology into broad commercial use. The aim of this article is not to comprehensively review recent work, but to provide commentary on recent successes and forecast where researchers should look to enhance the efficiency of photovoltaics. By lowering the LUMO level, utilizing electron‐withdrawing substituents advantageously, and employing appropriate side chains on donor polymers, researchers can elucidate further aspects of polymer‐PCBM interactions while ultimately developing materials that will push past 10% efficiency. 相似文献
6.
7.
Mylene M UyShinji Ohta Mihoko YanaiEmi Ohta Toshifumi HirataSusumu Ikegami 《Tetrahedron》2003,59(6):731-736
Three new spirocyclic sesquiterpenes designated exiguamide (1), exicarbamate (2) and exigurin (3), together with (−)-10-epi-axisonitrile-3 (4), have been isolated from the marine sponge Geodia exigua. All four compounds possess the spiro[4.5]decene skeleton and their structures were determined on the basis of spectroscopic data. The structure of 1 was confirmed by X-ray crystallographic analysis and the absolute configuration was determined by applying the modified Mosher's method on its amine derivative. Exiguamide (1) inhibited cell fate specification during sea urchin embryogenesis at a minimum inhibitory concentration of 0.4 μM. 相似文献
8.
Nguyen Xuan Uy 《Arkiv f?r Matematik》1979,17(1):19-27
9.
Uy. I. Babenko 《Journal of Mathematical Sciences》2002,110(4):2769-2773
The paper is an addition to the paper of Yu. I. Babenko and V. A. Zalgaller published in the same volume. It gives a condition under which the set of all vertices of several coaxial prisms inscribed in a sphere in
has power invariants I1,...,In. A finite set in
with 11 invariants is constructed. It is also proved that unions of prisms yield finite sets in
with any preassigned number n of invariants with alternating signs. Bibliography: 5 titles. 相似文献
10.
Nicolas Privault Wayne Isaac Uy 《Methodology and Computing in Applied Probability》2013,15(3):511-524
This paper is concerned with the Monte Carlo numerical computation of the Laplace transform of exponential Brownian functionals. In addition to the implementation of standard integral formulas, we investigate the use of various probabilistic representations. This involves in particular the simulation of the hyperbolic secant distribution and the use of several variance reduction schemes. The performance of those methods and their conditions of application are compared. 相似文献