The synthesis and high optical birefringence of nematogens incorporating 2,6-disubstituted naphthalenes and terminal cyano-substituent

A range of nematogenic materials which incorporate a 2,6-disubstituted naphthyl moiety and a terminal cyano-substituent have been synthesized by using palladium-catalysed cross-coupling procedures involving arylboronic acids and alkynylzinc reagents with aryl iodides, bromides and trifluoromethanesulphonates (triflates). The compounds have very high nematic phase stability, but their melting points are also quite high. The birefringences were measured using an extrapolation technique and the values were found to be between 0·26 and 0·42.     

Multi-level optical data storage in a photobleaching polymer using two-photon excitation under continuous wave illumination

A multi-level recording method is implemented in a photobleaching polymer using two-photon excitation under continuous wave illumination. It is experimentally shown that information encoded with ten levels of darkness can be successfully stored. This multi-level bit optical data storage method is of importance in increasing the storage density of a recording material and the speed of data access.     

Synthesis and biological evaluation of (-)-dictyostatin and stereoisomers

Total syntheses of (−)-dictyostatin, 6,16-bis-epi-dictyostatin, 6,14,19-tris-epi-dictyostatin, and a number of other isomers and analogs are reported. Three main fragments—top, middle, and bottom—were first assembled and then joined by olefination or anionic addition reactions. After appending the two dienes at either end of the molecule, macrolactonization and deprotection completed the syntheses. The work proves both the relative and absolute configurations of (−)-dictyostatin. The compounds were evaluated by cell-based measurements of increased microtubule mass and antiproliferative activity, and in vitro tubulin polymerization assays as well as competitive assays with paclitaxel for its binding site on microtubules. These assays showed dictyostatin to be the most potent of the agents and further showed that the structural alterations caused from 20- to >1000-fold decreases in activity.     

Phenole

Ohne Zusammenfassung     

More eigenvalue estimates

Estimates of the eigenvalues of the Sturm-Liouville problem —y+q(x)y = λy₁y(0) = 0 = y(1) are obtained by making linear approximations of q(x) over subintervals of [0, 1] when q(x) has a bounded second derivative.     

Gluings of modular lattices

The notions of gluing, tolerance relations, and Mal'cev products of varieties have been used by various authors to investigate varieties of lattices. In this paper the authors introduce a general framework for all these concepts and apply it to varieties of modular and Arguesian lattices.