Local geometry of arterial branchingZamir, M.
doi: 10.1007/BF02462270pmid: 7150813
Abstract A model of the geometrical structure of arterial bifurcations is proposed in the context of optimality of the bifurcation as a fluid conducting system. Optimality is considered both globally, in terms of the cardiovascular system as a whole, and locally, in terms of the orderliness of the flow in the bifurcation region. It is shown that a bifurcation can be optimal both globally and locally. Typical examples of such bifurcations are given.
Peak drug levels in linear pharmacokinetic systems—III. Multimodal impulse responses in multicompartment systemsThron, C. D.
doi: 10.1007/BF02462271pmid: 7150814
Abstract This paper deals with the unimodality of the ‘impulse response’ in compartmental systems, where the ‘impulse response’ in any given compartment is the time course of the amount of diffusing substance in that compartment after an initial instantaneous injection of the substance into that or some other compartment. It is shown that in certain compartmental structures, with injection in certain compartments, the impulse response is always unimodal or monotonic in all compartments, regardless of the numerical values of the various transfer rate coefficients. Structures with this property are here named ‘UM structures’, and they include the familiar mammillary and catenary structures. In this paper, the set of all UM structures is described. Structures which are not UM (NUM structures) are identified by showing that, by removal of certain connections and compartments according to certain rules, they can be reduced to small structures which can be shown to be NUM by numerical computation. Computations on two systems with bimodal impulse responses show that with constant infusions of a fixed amount of substance the peak level may increase paradoxically with decrease in the infusion rate over a certain range. This effect is extremely small, however.
Simulation of chemical oscillations in membranesStetson, R. F.;Hogan, W. A.
doi: 10.1007/BF02462272pmid: 7150815
Abstract A computer simulation model has been developed to follow chemical oscillations in a membrane for immobilized enzyme systems. It is a discrete particle type model which follows the spatial and temporal fluctuations of the concentrations in a reaction involving two substrates. The parameters can be readily varied to allow dissipative structures to result from the sustained nonlinear reaction kinetics and to determine which parameters cause damping of the oscillations. The nature of the diffusion mechanism allows extension to more than one dimension.
An eight-parameter model of human mortality—The single decrement caseMode, Charles J.;Busby, Robert C.
doi: 10.1007/BF02462273pmid: 7150816
Abstract Developed in this paper is an eight-parameter model of human mortality. A step-wise nonlinear least-squares procedure for estimating the parameters from abridged life tables is also described and implemented. Used for purposes of illustration were nine period life tables, ranging from 1900 to 1977, for the United States white male population. The agreement between the observed and calculated survival functions in the nine life tables was very good. Apart from its phenomenological interest, the model provides an effective means for calculating interpolations and extrapolations of abridged life tables, which are useful making population projections and in computer graphics.
Representations of (M, R)-systems by categories of automataWarner, M. W.
doi: 10.1007/BF02462274pmid: N/A
Abstract Arbib in a paper entitled ‘Categories of (M, R)-Systems' represents both simple (M, R)-systems and those with varying genome as subcategories of the category of automata. An alternative characterisation of general (M, R)-systems as automata is proposed and two theorems on (M, R)-automata are proved. The two categories of automata, namely Arbib in a paper entilled ‘Categories of (M,R)-Systems’ represents both simple (M, R)-systems with variable genetic structure, are compared.
Equilibrium electropotentials in electrolyte systemsMarshall, E. A.
doi: 10.1007/BF02462275pmid: 7150817
Abstract The determinationof electric potentials in finite regions of symmetrical electrolyte in one-dimensional equilibrium situations requires the solution of the one-dimensional Poisson-Boltzmann equation in which the dependent variable is linearly related to the electric potential and contains unknown parameters. These require evaluation as part of the solution to a given boundary value problem. The general solution of the equation is presented. This involves elliptic functions and integrals and is sectionally isomorphic with respect to an integration parameter. The application to problems posed in terms of both initial values and two-point boundary values is discussed. The solution is used to determine the potential and concentration distributions between two flat-faced charged particles immersed in an electrolyte liquid and having interacting double layers.
Evolution of a predator-prey Volterra-Lotka ecosystem with saturation effectHirata, Hironori
doi: 10.1007/BF02462277pmid: 7150818
Abstract This paper has studied the evolution of a predator-prey Volterra-Lotka ecosystem with saturation effect for the general case where both predator and prey evolve. We have interesting results under the evolutional condition, as follows: (1) the predator population and the ratio of predator to prey populations increase; (2) the parameters of the prey drift in the direction of increasing multiplication rate and saturation level, while the parameters of the predator drift in the direction of decreasing death rate.
Solitary waves and macromolecular systemsBhaumik, Debajyoti;Dutta-Roy, Binayak;Lahiri, Avijit
doi: 10.1007/BF02462278pmid: N/A
Abstract Macromolecules and their aggregates (such as protein bundles in biomembranes) possess polar modes which, when excited, tend to deform the system and call into play elastic restoring forces. A model of such systems, characterised typically by electric polarisation modes stabilised on the one hand by quartic self-interactions and on the other through coupling to the elastic deformations, admits the possibility of localised excitations (solitary waves) propagating with subsonic velocities, possessing the features of relative stability and efficient transport characteristics (associated with the collective nature of the phenomena), and at the same time provides a mechanism of control and variability which could be of considerable interest in biology.