PubMed Health⌕ Search

Biomedical subjects

H M Hastings

Publications and source records attributed to H M Hastings.

8 recordsLinked to original sources
PubMed1992

Statistical geometry of pancreatic islets.

Quantitative histomorphometric studies of the dynamics of growth and development of pancreatic islets in normal and pathological states pose substantial methodological and conceptual problems. We address these problems with the geometry of random fractals, and apply our methods to the analysis of islet regeneration in the alloxan-treated guinea-pig. In both experimental islet-regenerated and control animals, islet centres are found to cluster in similar fractal subsets of dimension strictly less than 3, in agreement with the postulated origin of islets along a system of ductules, and suggesting that regeneration follows the same mathematical dynamics as original islet formation.

Alloxan↗
PubMed1991

Remarks on population planning and control.

We investigate the use of control theory in population planning and show how the use of age at first birth, birth interval, and sex ratio as control variables leads to a practical, fault tolerant approach to population planning and control.

Age Factors↗
PubMed1989

Evolutionary learning and hierarchical Markov systems.

The observation is made that various forms of evolutionary learning systems and classical evolutionary processes can be formally described as hierarchical systems of Markov processes. This leads to a simplification of issues such as convergence criteria and limiting behavior of such systems. The hierarchical structures in question are derived from the notion of rules and meta-rules for moving on graphs studied previously.

Biological Evolution↗
PubMed1989

Sixty million connections per second.

The purpose of this note is to report processing in a feedforward neural network at a peak speed of 59.9 million connections per second. The network algorithm was coded in Fortran and executed on a CRAY XMP-1, a high speed general purpose vector machine.

Artificial Intelligence↗
PubMed1986

Sex and computing.

The computational power of asexual and sexual reproduction is explored with the conclusion that sexual reproduction probably offers significantly greater computational power. This at least partially explains the evolution of sex.

Biological Evolution↗
PubMed1985

Low dissipation computing in biological systems.

Biological systems frequently need to solve many computationally hard decision and optimization problems. The solution of these problems by digital computers as presently understood requires exponentially large energy dissipation. This severely restricts the ability of digital computers to attack such problems. We shall show that only polynomial dissipation is required to solve these problems adequately by "physical annealing", as realized in the genetic system, making these problems tractable energetically.

Biometry↗