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961.
Squier AH Airs RL Hodgson DA Keely BJ 《Rapid communications in mass spectrometry : RCM》2004,18(23):2934-2938
Atmospheric pressure chemical ionisation reversed-phase high-performance liquid chromatography/multistage mass spectrometry has been used to study the mass spectral fragmentation of the cyanobacterial sheath pigment scytonemin and its reduced counterpart. The two pigments exhibit characteristic fragment ions in their MS2 and MS3 spectra that are of value in confirming the identification of the structures in extracts from natural environments. 相似文献
962.
Angela Pistoia Olivier Rey 《Calculus of Variations and Partial Differential Equations》2003,18(3):243-251
Let
,
, be a bounded domain as defined by Flucher, Garroni and Müller [6], which has a singular point
such that the Robins function achieves its infimum at
. Considering the elliptic problem
in
; u = 0 on
, with p = (N + 2)/(N-2),
, and
a minimizing solution of
,
concentrates at
as
goes to zero.Received: 15 September 2002, Accepted: 5 November 2002, Published online: 16 May 2003Mathematics Subject Classification:
35J65Angela Pistoia: The author is supported by M.U.R.S.T., project Metodi variazionali e topologici nello studio di fenomeni non lineari 相似文献
963.
Sensitivity-enhanced versions of the IPAP, TROSY-anti-TROSY, and E.COSY experiments for measuring one-bond 15N-1HN couplings are presented. Together with the previously developed sensitivity-enhanced E.COSY-type HSQC experiment they comprise a suite of sensitivity-enhanced experiments that allows one to chose the optimal spectrum for accurate measurement of one-bond 15N-1HN residual dipolar couplings in proteins. Since one-bond 15N-1HN residual dipolar couplings play uniquely important roles in structural NMR, these additional methods provide further tools for improving structure determination of proteins and other biological macromolecules. 相似文献
964.
[reaction: see text] The stereochemistry of the cyclobutanones 3, obtained by lithium salt catalyzed ring expansion of the optically pure oxaspiropentanes 2, depends not only on the lithium salt but also on the stereochemistry of 2. They constitute the starting material for the syntheses of the acetogenin (-)-(4R,5R)-muricatacin and the pheromone (R)-japonilure. 相似文献
965.
Campagnuolo C Fattorusso C Fattorusso E Ianaro A Pisano B Taglialatela-Scafati O 《Organic letters》2003,5(5):673-676
Simplakidine A, a unique 4-alkyl-substituted pyridiunium alkaloid, has been isolated from the Caribbean sponge Plakortis simplex. The stereostructure of simplakidine A has been determined using MS and NMR data, molecular mechanics, and an extension of the J-based configuration analysis. Data about the growth-inhibition activity of simplakidine A are reported. 相似文献
966.
Angela Kopp 《Annals of Physics》2007,322(6):1466-1476
We propose that quantum phase transitions are generally accompanied by non-analyticities of the von Neumann (entanglement) entropy. In particular, the entropy is non-analytic at the Anderson transition, where it exhibits unusual fractal scaling. We also examine two dissipative quantum systems of considerable interest to the study of decoherence and find that non-analyticities occur if and only if the system undergoes a quantum phase transition. 相似文献
967.
968.
Novel transformation products of chlorophyll a incorporating a methyl sulfide group in the substituent at the C-3 position have been identified in Recent sediments from an Antarctic lake. 相似文献
969.
Angela A. Albanese 《Proceedings of the American Mathematical Society》2000,128(2):583-588
For coechelon spaces of infinite order it is proved that every compact subset of is contained in a closed absolutely convex hull of some null sequence if and only if the matrix is regularly decreasing.
970.
We etablish a necessary and sufficient condition under which there exists a tangential and well graded star product, differential or not, on the dual
of a nilpotent Lie algebra
. We also give enlightening examples with explicit computations. 相似文献