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831.
Pedersen HT Bro R Engelsen SB 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2002,157(1):141-155
In this work an alternative method, named SLICING, for two-dimensional and noniterative T(2) decomposition of low-field pulsed NMR data (LF-NMR) is proposed and examined. The method is based on the Direct Exponential Curve Resolution Algorithm (DECRA) proposed by W. Windig and A. Antalek (1997, Chemom. Intell. Lab. Syst.37, 241-254) and takes advantage of the fact that exponential decay functions, when translated in time, retain their characteristic relaxation times while only their relative amounts or concentrations change. By such simple translations (slicing) it is possible to create a new "pseudo" direction in the relaxation data and thus facilitate application of trilinear (multiway) data-analytical methods. For the application on LF-NMR relaxation data, the method has two basic requirements in practice: (1) two or more samples must be analyzed simultaneously and (2) all samples must contain the same qualities (i.e., identical sets of distinct T(2) values). In return, if these requirements are fulfilled, the SLICING (trilinear decomposition) method provides very fast and unique curve-resolution of multiexponential LF-NMR relaxation curves and, as a spin-off, calibrations to reference data referring to individual proton components require only scaling of the resulting unique concentrations. In this work the performance of the SLICING method (including multiple slicing schemes) is compared to a traditional two-dimensional curve fitting algorithm named MATRIXFIT through application to simulated data in a large-scale exhaustive experimental design and the results validated by application to two small real data sets. Finally a new algorithm, Principal Phase Correction (PPC) based on principal component analysis, is proposed for phase rotation of CPMG quadrature data, an important prerequisite to optimal SLICING analysis. 相似文献
832.
Carol E. Parker Maurice M. Bursey Lee G. Pedersen 《Journal of mass spectrometry : JMS》1973,7(9):1077-1081
INDO calculations for previously proposed activated complexes for scrambling in ethane molecular ion suggest that the structure equivalent to diborane is more stable than one in which hydrogens on the same side of the molecule exchange positions. 相似文献
833.
J Lau E B Pedersen C M Nielsen 《Acta chemica Scandinavica (Copenhagen, Denmark : 1989)》1991,45(6):616-620
Mercuric-catalyzed hydrolysis of acetylated L-rhamnal 1 gives an alpha,beta-unsaturated aldehyde 2. 1,4-Addition of DBU-phthalimide salt with concomitant acetyl shift resulted in L-ribo and L-arabino isomers of 5-O-acetyl-2,3,6-trideoxy-3-phthalimido-hexofuranose 3 and 4. After acetylation at the anomeric center, coupling with silylated thymine resulted in three new nucleosides, with L-acosamine and L-ristosamine of furanose configuration as the carbohydrate moiety. The target compounds have been evaluated for their antiviral activity against HIV and HSV-1. 相似文献
834.
835.
5′-O-(4,4′-dimethoxytrityl)-5-methyl-N4-(1-pyrenylmethyl)cytidine(5) was prepared by reaction of 1-pyrenylmethylamine with an appropriate protected 4-(1,2,4-triazolyl)thymidine derivative which was synthesized from 5-O-DMT protected thymidine by acetylation with acetic anhydride and subsequent reaction with triethylamine, 1,2,4-triazole and POCl3. Stabilities are reported for DNA duplexes, three-way junctions and triplexes when 5 is inserted. Most interestingly, the three-way junctions are stabilized when 5 is used for insertion into the junction region. This break-through for recognizing the foot of a stem could have far-reaching importance because new targets for antisense oligos is now rendered possible on intact secondary structures. 相似文献
836.
Henrik?JensenEmail author Karsten?D.?Joensen Jens-Erik?J?rgensen Jan?Skov?Pedersen G.?S?gaard 《Journal of nanoparticle research》2004,6(5):519-526
A thorough analysis of nanosized partly crystalline photocatalysts has been carried out. X-ray diffraction (XRD), Small angle X-ray Scattering (SAXS), Scanning electron microscope (SEM), and BET measurements have been applied to study the particle properties of different photocatalysts. The study permitted the determination of absolute crystallinity of partly and fully crystalline photocatalysts by XRD. The absolute crystallinity was determined with CaF2 as a reference. SAXS measurements were used to study the morphology and to determine the primary particle size of the investigated photocatalysts. The study showed that the commercially available photocatalyst Hombikat UV100 consisted of a great fraction of amorphous material whereas Degussa P25 was found to be almost crystalline. A homemade sample was found to be 63% crystalline anatase and 37% amorphous. The study also revealed that there was a deviation between the primary particle size and the crystal size for the partly crystalline samples caused by the amorphous fraction; however, the fully crystalline Degussa P25 had agreement between the primary particle size and the crystal size. 相似文献
837.
S.?Madsen G.?FilatrellaEmail author N.?F.?Pedersen 《The European Physical Journal B - Condensed Matter and Complex Systems》2004,40(2):209-215
The electrical behavior of anisotropic BSCCO single crystals is modeled by mutually coupled long Josephson junctions. We show
that although the fluxons in the different layers do not a priori prefer the in-phase motion desired for many potential applications
it is possible to induce such behavior by coupling the system to a high-Q resonator with a resonance frequency corresponding
to fluxon in-phase motion. The resulting model is a set of coupled non-linear partial differential equations. By direct numerical
simulations we have demonstrated that the qualitative behavior of the combined stacked long Josephson junctions and cavity
system can be understood on the basis of the general concepts of nonlinear oscillators interacting with a resonator. For some
region of the parameter space it is possible to reach the desired synchronous state, making the system potentially suitable
for applications. We also look at the different dynamical states defined by different fluxon dynamical states in combination
with different cavity properties. 相似文献
838.
Pere?AraEmail author Gert?K.?Pedersen Francesc?Perera 《Algebras and Representation Theory》2005,8(1):75-97
We prove a new extension result for QB-rings that allows us to examine extensions of rings where the ideal is purely infinite and simple. We then use this result to explore various constructions that provide new examples of QB-rings. More concretely, we show that a surjective pullback of two QB-rings is usually again a QB-ring. Specializing to the case of an extension of a semi-prime ideal I of a unital ring R, the pullback setting leads naturally to the study of rings whose multiplier rings are QB-rings. For a wide class of regular rings, we give necessary and sufficient conditions for their multiplier rings to be QB-rings. Our analysis is based on the study of extensions and the use of nonstable K-theoretical techniques.
Presented by S. MontgomeryMathematics Subject Classification (2000) 16D30.Gert K. Pedersen: Deceased 15 March 2004.Partially supported by the DGI and European Regional Development Fund, jointly, through Project BFM 2002-01390, the Comissionat per Universitats i Recerca de la Generalitat de Catalunya and the Danish Research Council. 相似文献
839.
Andersen ML Ruhwald M Thorn M Pedersen AE Mathiassen S Buus S Claesson MH 《Journal of immune based therapies and vaccines》2003,1(1):1
Thirteen H-2b-binding peptides derived from six potentially overexpressed proteins in p53-/- thymoma (SM7) cells were studied for immunogenecity and vaccine-induced prevention of tumor growth in mice inoculated with SM7 tumor cells. Six of the peptides generated specific CTL responses after immunization, but only two of these peptides (RAD23-31 and RAD24-31) were capable of generating a weak vaccination-induced protection against adoptive tumor growth. SM7 inoculated mice treated with a blocking antibody against the inhibitory T cell signal transducing molecule CTLA4 appeared to delay tumor take, suggesting that SM7 thymoma cells are recognized by the adaptive immune system of the host. However, prophylactic vaccination with RAD23-31 and RAD24-31 peptides combined with anti-CTLA4 Ab treatment and did not improve tumor resistance. Our data would indicate that vaccination with immunogenic peptides derived from potentially overexpressed tumor proteins, as identified by mRNA expression profiling of p53-/- thymoma cells, at best results in a weak tumor protection thus questioning this way of detection of new tumor rejection epitopes. 相似文献
840.
Lammich L Strasser D Kreckel H Lange M Pedersen HB Altevogt S Andrianarijaona V Buhr H Heber O Witte P Schwalm D Wolf A Zajfman D 《Physical review letters》2003,91(14):143201
We demonstrate that the dissociative recombination of D2H+ with low-energy electrons depends on the rotational energy of the molecular ion such that highly excited ions have a larger rate coefficient than colder ones. Observations on an ion beam continuously interacting with electrons at low relative velocity indicate that excited rotational levels are preferentially depleted which, in competition with radiative heating due to blackbody radiation, provides an opportunity for controlling the rotational temperature of stored molecules. 相似文献