Dual Conjugate Research Articles

Synthesis and Binding Properties of Calix[4]Arene Dual Porphyrin Conjugate: Tweezers for DABCO

A dual porphyrin system built on a calix[4]arene spacer was prepared and the corresponding Zn(II) complex 4 showed a marked affinity for 1,4-diazobicyclo[2.2.2]octane (DABCO) as compared with other amines.

Computational comparisons of dual conjugate gradient algorithms for strictly convex networks

This paper presents a Lagrangian dual conjugate gradient algorithm for solving a variety of nonlinear network problems with strictly convex, differentiable, and separable objective functions. The proposed algorithm belongs to an iterative dual scheme, which converges to a point within a given tolerance-relative residual error. By exploiting the special structure of the network constraints, this approach is able to solve large problems with minimal computer memory requirements because no matrix operations are necessary. An extensive computational study has been carried out using different direction generators, line search procedures, and restart schemes. Two conjugate gradient direction formulas, the Polak-Ribière and the memoryless BFGS, have been compared. In addition, two restart methods—the Beale's restart and the gradient restart—are tested for their effectiveness. A Newton method line search was tested against a bisection line search. Computational comparisons using statistical analysis have also been reported to illustrate the effectiveness of each combination of these procedures. The proposed method works well for network problems with quadratics, entropy, cubic, polynomial, and logarithm types of objective functions. Our computational experiments indicate that the most effective Lagrangian dual algorithm should include the combination of the Polak-Ribière conjugate gradient formula, the Newton line search, and the gradient restart.

Biologic Activity of a Nucleotide Conjugate Between Mitomycin C and Cytarabine Monophosphate

Abstract A dual prodrug conjugate between the antimetabolite cytarabine monophosphate and the alkylating agent 2,7-diaminomitosene (derived from mitomycin C), cytaramycin, was synthesized and tested for antileukemic activity in sensitive and resistant tumors. The compound was active against parental L-1210, CCRF-CEM, HL-60 and K-562 leukemia cells but did not overcome resistance in sublines developed for (1) multidrug resistance (L-1210/MDR and K-562-R) or (2) for cytarabine resistance (CCRF-CEM/ARA-C and HL-60/ARA-C). Alkaline DNA elution tests demonstrate a predominance of strand breaking activity due to the cytarabine moiety, and a lesser degree of DNA crosslinking, due to the mitosene moiety. The conjugate was active in mice bearing P-388 leukemia (80% increased lifespan), but was not more effective than mitomycin C alone in mice bearing a cytarabine-resistant L-1210 cell line (38% to 31% increased lifespan). These findings suggest that mitomycin nucleotide conjugates do not overcome resistance to the...

Discussion of Dr JØrgensen’s Paper

Discussion of Dr JØrgensen’s Paper

Link formulation of lattice spin systems

In analogy with the recent plaquette formulation of lattice gauge theory, we develop lattice spin systems in terms of links, with all correlations in terms of lattice Bianchi identities. On finite lattices (periodic and twisted), new global (topological) Bianchi identities are found. The dual variables conjugate to these global identities are essentially the spin analog of 't Hooft's dual variables.