Scrambling in ethane molecular ion: An INDO model for hydrogen exchange before mass spectral fragmentation

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.     

Synthesis and evaluation of antiviral activity of L-acosamine and L-ristosamine nucleosides of furanose configuration.

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.     

Insertion of 5-methyl-N-(1-pyrenylmethyl)cytidine into DNA. Duplex, three-way junction and triplex stabilities

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.     

Characterization of nanosized partly crystalline photocatalysts

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.     

Interaction between a BSCCO-type intrinsic Josephson junction and a microwave cavity

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.     

Extensions and Pullbacks in QB-Rings

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.     

Dynamic Jahn-Teller effects in isolated C60- studied by near-infrared spectroscopy in a storage ring

We have measured the near-infrared absorption spectrum for isolated C60- ions at room temperature. Two bands, at 9145 cm(-1) and 10460 cm(-1), have been identified in addition to the main absorption band at 9382 cm(-1), seen also at low temperature in a matrix. An interpretation based on the theory of dynamic Jahn-Teller effects is proposed.     

Mechanics of the turbulent-nonturbulent interface of a jet

We report the results of an experimental investigation of the mechanics and transport processes at the bounding interface between the turbulent and nonturbulent regions of flow in a turbulent jet, which shows the existence of a finite jump in the tangential velocity at the interface. This is associated with small-scale eddying motion at the outward propagating interface (nibbling) by which irrotational fluid becomes turbulent, and this implies that large-scale engulfment is not the dominant entrainment process. Interpretation of the jump as a singular structure yields an essential and significant contribution to the mean shear in the jet mixing region. Finally, our observations provide a justification for Prandtl's original hypothesis of a constant eddy viscosity in the nonturbulent outer jet region.     

Tumor-associated antigens identified by mRNA expression profiling as tumor rejection epitopes

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.