Biomedical subjects

D Lukman

Publications and source records attributed to D Lukman.

3 recordsLinked to original sources

PubMed1999

Criticality of D=2 and D=3 Ising models: cluster structure versus populations.

The energy and the specific heat of two- and three-dimensional Ising systems are analyzed in terms of cluster properties. The energy and the specific heat are decomposed into two components, which are defined by quantities pertaining to cluster populations and cluster structure expressed in terms of average cluster perimeters. It is shown that the structural component of the energy as well as of the specific heat represents the dominant contribution. Indications are presented that the critical exponent of structural and populational components of specific heat matches the exponent of the entire specific heat.

Journal Article↗

PubMed1994

Tandemly repeated pentanucleotides in DNA sequences of eucaryotes.

Genetic sequence data banks were scanned in order to retrieve tandemly repeated pentanucleotides (pnts). It was found that among 102 (=(1024-4)/2/5) possible distinct pnts roughly each fourth is involved in tandem repeats. It is shown that tandemly repeated pnts are composed of frequently occurring di- and trinucleotides and that those pnts which occur frequently in the form of mono- or di-pnts form also tandem repeats either in the form of satellites or in the form of shorter tandem repeats. Human satellite III is taken as a specific example. It is shown that the first guanine within GG-AAT pnt exhibits the highest mutability. Sequential distribution of base changes gives evidence that the mutations do not occur at random positions but in a correlated fashion so that long stretches of original pnts remain intact. It is found that pnts related to the satellite III are present in introns and flanking regions of some structural genes, but are not preserved between orthologous genes of related species. The results corroborate the most plausible mechanism of their evolution--rapid amplification followed by successive divergence of repeat units by various mutational processes.

Animals↗

PubMed1991

Knowledge-based schedule formulation and maintenance under uncertainty.

This paper is concerned with the dual sequential problems of (1) determining an acceptable personnel schedule over a specified time period, and (2) adjusting that schedule during the course of its execution in reaction to daily changes in both demand and available personnel. The first problem is schedule formulation; the second sequential problem is schedule execution. A rule-based, hierarchical system has been developed for first modeling and then solving both the schedule formulation and the schedule execution problems as a two-phase dependent process. The system is applied to the scheduling and staffing of nurses. A double-blind evaluation was conducted, which ascertained the quality of the resultant schedules in terms of maintainability, coverage, and personal satisfaction. The evaluation indicates that for units on which personnel changes have occurred, the prototype appears to perform as well as human schedulers.

Humans↗