Some Properties of Solutions to the Novikov Equation with Weak Dissipation Terms

In this paper, we investigate the Novikov equation with weak dissipation terms. First, we give the local well-posedness and the blow-up scenario. Then, we discuss the global existence of the solutions under certain conditions. After that, on condition that the compactly supported initial data keeps its sign, we prove the infinite propagation speed of our solutions, and establish the large time behavior. Finally, we also elaborate the persistence property of our solutions in weighted Sobolev space.     

The relative canonical algebra for genus 4 fibrations

In this paper, we prove that for the genus 4 fibration, the relative canonical algebra is generated in degrees 3.     

Simultaneous determination of uric acid, xanthine and hypoxanthine with an electrochemically pretreated carbon paste electrode

A simple method is presented for the simultaneous differential pulse voltammetric determination of uric acid, xanthine and hypoxanthine. It is based on the improved current responses of the three analytes at carbon paste electrodes polarized in a dilute alkaline medium (0.002 mol/l NaOH, 0.1 mol/l NaClO₄) at 1.3 V vs. SCE for a short time. Compared with the methods reported in the literature, this procedure has a much wider linear range (2 to 3 orders of magnitude in concentration), lower detection limits (5 to 10 g l^–1) and less interference by ascorbic acid. The electrochemical responses were found to be dependent on the pre-anodization potential and the time imposed on the electrodes as well as on the alkalinity of the supporting electrolyte. The proposed procedure was used to determine uric acid, xanthine and hypoxanthine in human urine without any preliminary treatment.     

Highly Efficient and Practical Syntheses of Lavendamycin Methyl Ester and Related Novel Quinolindiones

The novel 7-(N-formyl-, 7-(N-acetyl-, and 7-(N-isobutyrylamino)-2-methylquinoline-5,8-diones were synthesized in excellent overall yields in three steps via the nitration of the commercially available 8-hydroxy-2-methylquinoline followed by a reduction-acylation step and then oxidation. Acid hydrolysis of 7-(N-acetylamino)-2-methylquinoline-5,8-dione (14a) afforded the novel 7-aminoquinoline-5,8-dione 7 in excellent yields. Due to our efficient preparation of dione 14a, we now report a short and practical method for the total synthesis of the potent antitumor agent lavendamycin methyl ester (1b) with an excellent overall yield.     

Structures formed by the chiral assembly of racemic mixtures of enantiomers: iodination products of elaidic and oleic acids

The self-assembled monolayer structure of the products of elaidic acid iodination (the racemic mixture of 9,10-(9S,10R)-diiodooctadecanoic acid and 9,10-(9R,10S)-diiodooctadecanoic acid) and the products of oleic acid iodination (the racemic mixture of 9,10-(9R,10R)-diiodooctadecanoic acid and 9,10-(9S,10S)-diiodooctadecanoic acid) are studied by high-resolution scanning tunneling microscopy. For the iodination products of elaidic acid, the separation of enantiomers into distinct chiral domains during the formation of the 2-D crystal on the highly ordered pyrolytic graphite (HOPG) surface is not observed. Instead, within the diiodooctadecanoic acid SAM, each row of molecules is composed of opposite racemates. The two opposite racemates pack alternately inside a row, using different faces to adsorb on the surface. The unit cell is composed of a pair of opposite racemates, forming a heterochiral structure. For the iodination products of oleic acid, the racemic mixture is observed to exhibit quasi-phase separation during the formation of the 2-D crystal on the HOPG surface. Each row is composed of homochiral acid molecules, either the 9,10-(9R,10R)-diiodooctadecanoic acid (R) or the 9,10-(9S,10S)-diiodooctadecanoic acid (S). The R row and the S row pack alternately, with a unit cell composed of four molecules. Two of the molecules in the unit cell are the 9,10-(9R,10R)-diiodooctadecanoic acid (R) molecules; two are the 9,10-(9S,10S)-diiodooctadecanoic acid (S) molecules. In the unit cell, the two molecules that have the same chirality pack antiparallel inside the homochiral row, using different faces to adsorb on the surface. These results suggest that several different types of chiral assembly are possible. Enantiomers with opposite chirality exhibit many chiral assembly patterns, forming heterochiral structures on the surface in addition to separation to form macroscopic chiral domains. By using different conformations, similar enantiomers with opposite chirality will display many chiral assembly patterns to form heterochiral structures on the surface.     

Direct observation of eta 2-imine formation through beta-H abstraction between amide ligands. Neutron and X-ray diffraction structure of a dihydride imine ditantalum complex

Reactions of Ta(NMe2)5 with D2SiR'Ph (R' = Me, Ph) were found to give a dideuteride eta 2-imine complex (Me2N)3Ta(mu-D)2(mu-N-eta 2-N,C-CH2NMe)Ta(NMe2)3(1-d2) through C-H activation of an amide ligand via beta-H abstraction, and the structure of 1 was confirmed by single crystal neutron and X-ray diffraction.     

A new synthesis of 2-fluoro-1-naphthols

A general synthesis of 2-fluoro-1-naphthols in two steps from 1-indanones is reported. The 1-indanones are first converted to difluoromethyl 2-fluoro-1-napthyl ethers by reaction with difluorocarbene source, trimethylsilyl 2-fluorosulfonyl-2,2-difluoroacetate (TFDA). These ethers are then converted in high yield to the respective naphthols by heating with a mixture of acetic acid and 48% HBr.