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1.
Eduardo D. Sontag 《Systems and synthetic biology》2007,1(2):59-87
Monotone subsystems have appealing properties as components of larger networks, since they exhibit robust dynamical stability
and predictability of responses to perturbations. This suggests that natural biological systems may have evolved to be, if
not monotone, at least close to monotone in the sense of being decomposable into a “small” number of monotone components,
In addition, recent research has shown that much insight can be attained from decomposing networks into monotone subsystems
and the analysis of the resulting interconnections using tools from control theory. This paper provides an expository introduction
to monotone systems and their interconnections, describing the basic concepts and some of the main mathematical results in
a largely informal fashion.
Supported in part by NSF Grants DMS-0504557 and DMS-0614371. 相似文献
2.
I. Opatowski 《Bulletin of mathematical biology》1945,7(4):161-180
A mathematical theory applicable to the biological effects of radiations as chain processes is developed. The theory may be
interpreted substantially as a “hit theory” involving the concepts of “sensitive volume” or “target area”. The variability
of the sensitivity of the organism to the radiation and its capacity of recovery between single hits is taken into account.
It is shown that in a continuous irradiation of a biological aggregate in which the effect of each single hit cannot be observed,
recovery and variation of sensitivity are formally equivalent to each other so that a discrimination between these two phenomena
is possible only by discontinuous irradiation or by using different radiation intensities. Methods for the calculation of
the “number of hits” and for the determination of the kinetics of the processes from “survival curves” or similar experimental
data are given. The relation between the recovery and the Bunsen-Roscoe law is discussed. The case in which the injury of
the organism is dependent on the destruction of more than one “sensitive volume” is also considered. 相似文献
3.
Robert Rosen 《Bulletin of mathematical biology》1958,20(4):317-341
A mathematical framework for a rigorous theory of general systems is constructed, using the notions of the theory of Categories
and Functors introduced by Eilenberg and MacLane (1945,Trans. Am. Math. Soc.,58, 231–94). A short discussion of the basic ideas is given, and their possible application to the theory of biological systems
is discussed. On the basis of these considerations, a number of results are proved, including the possibility of selecting
a unique representative (a “canonical form”) from a family of mathematical objects, all of which represent the same system.
As an example, the representation of the neural net and the finite automaton is constructed in terms of our general theory. 相似文献
4.
Anthony F. Bartholomay 《Bulletin of mathematical biology》1965,27(1):235-251
In an earlier paper (Molecular Set Theory: I.Bull. Math. Biophysics,22, 285–307, 1960) the author proposed a “Molecular Set Theory” as a formal mathematical meta-theoretic system for representing
complex reactions not only of biological interest, but also of general chemical interest. The present paper is a refinement
and extension of the earlier work along more formal algebraic lines. For example the beginnings of an algebra of molecular
transformations is presented. It also emphasizes that this development, together with the genetical set theory of Woodger's
and Rashevsky's set-theoretic contributions to Relational Biology, points to the existence of a biomathematical theory of
sets which is not deducible from the general mathematical, abstract theory of sets. 相似文献
5.
A mathematical model of HIV dynamics in the presence of a rescuing virus with replication deficiency
Recently, an enzyme (Cre recombinase) has been developed by directed evolution that successfully removes the HIV genome from
the nuclear DNA of infected cells. To explore this idea further, we hypothesized that a replication deficient virus (called
“police virus”), added externally, can deliver such a recombinase which excises the integrated HIV DNA from the genome of
infected cells. Such a “police virus” could attack and remove the integrated provirus which is not possible using contemporary
strategies. The hypothesis was tested by developing a mathematical model that describes the dynamics of virus-host cell interaction
and the consequences of introducing the “police virus”. The simulations show that such a therapeutic vector may eradicate
all HIV viruses from the system in the long term. All components of the HIV infection (free virus, latently, and actively
infected cells) can be cleared and the system ends up only with susceptible CD4+ cells. The proposed model may provide new
insights in the dynamical behavior and future alternative treatments of HIV. 相似文献
6.
Otto E. Rössler 《Bulletin of mathematical biology》1977,39(2):275-289
“Spiral-type chaos” and “screw-type chaos” constitute two simple types of nonperiodic oscillatory flow in 3-variable continuous
systems. The former type is exhibited, for example, by auniversal system in the switching mode, when the regimens of flow on the two stable branches of the slow manifold in state space are made
to differ in an appropriate manner. Screw-type chaos occurs in ahysteresis oscillator between two stable limit cycles, if the rotation gain is positive. For either case, an analogous 2-dimensional “branched
papersheet flow” exists. Both flows are determined by a single-variable discrete dynamical system of the Lorenz-Li-Yorke type
(as a cross-section), as well as by an equivalent new map. Numerical simulations of two abstract reaction systems giving rise
to non-idealized (that is, truly 3-dimensional) flows of either type are presented. The corresponding discrete dynamical systems
(Poincaré maps) are 2-dimensional now, having the form of a flattened hairpin (“horseshoe”) in the simplest case. Thus, two
actual examples for 3-dimensional flows suspended by a horseshoe diffeomorphism seem to have been found. One contains just
a single functionally effective nonlinearity. Real systems of either type may be found in physics, chemistry, biochemistry,
biophysics and economy. 相似文献
7.
This paper deals with information transfer from the environment and “self”-organization in open, nonlinear systems far from
thermodynamic equilibrium — in the presence of either non-stationary phase jitter noise, or amplitude stationary noise. By
“self”-organization we mean here the progressive formation within the system of sequential, ordered (coherent) relationships
between appropriate dynamical variables-like for example, the phase differences between the oscillating components of the
system. We take up (in Section II) the classical Laser as a specific example and examine in detail the influence of phase
jitter noise in the mode (phase) locking process. We find—as expected—that phase fluctuations in the cavity cause degradation
of the coherent behaviour (i.e. increase the entropy) of the system — which, however, levels off, or saturates with time.
Further (in Section III) we examine systems where the number of self-sustained oscillating components may vary with time in
such a way that the maximum entropy of the system increases faster than the overall instantaneous entropy. We put forth the
hypothesis that in such cases — because of the increase of the redundancy — the system gets organized not just in spite of,
but merely because of the presence of Noise. Possible applications in biological systems (especially concerning a model of
cerebral organization) are briefly discussed. It is understood here, that the system has to display some preliminary dynamical
structure before the organizing procedure takes over. What happens afterwards is the subject of this paper. 相似文献
8.
The relational structure of RNA, DNA, and protein bears an interesting similarity to the determination problem in category
theory. In this paper, we present this deep-structure similarity and use it as a springboard for discussing some abstract
properties of coding in various systems. These abstract properties, in turn, may shed light on the evolution of the DNA world
from a semiotic perspective. According to the perspective adopted in this paper, living systems are not information processing
systems but “meaning-making” systems. Therefore, what flows in the genetic system is not “information” but “value.” We define
meaning, meaning-making, and value and then use these terms to explain the abstract dynamics of coding, which can illuminate many forms of sign-mediated activities
in biosystems. 相似文献
9.
The recent mathematical formalization of the concepts of matter and extrinsical energy, which are used for the relational
representation of biological systems, is employed in the analysis of the important experimental discoveries of Comorosanet al. related to low energy electromagnetic irradiations on enzyme substrates. By means of the present analysis one of the properties
inherent to the experimental phenomena is more precisely exposed, and theoretical developments corresponding to “energetical
evolutions” in a biological system (Leguizamón, 1976) may now have an experimental basis.
Important limitations are introduced for the validity of the commutativity and associativity of cartesian product of sets,
when they represent matter and its linked extrinsical energy. In connection with this last aspect, new important knowledge
is obtained for the relational mathematical representation of biological systems. 相似文献
10.
The behavior of large systems of randomly-interacting variables is examined using an intentionally simplified model. The stable
positive solutions are found to exhibit to a significant degree some well-known properties of ecological systems. This resemblance
(including for example the predominance of “predator-prey” interactions) is all the more striking in view of the lack of biological
“data” at the input end. The findings suggest it advisable to distinguish two kinds of properties in ecosystems. One kind
would depend on specifically biological mechanisms; the other would characterize a wide class of persistent systems, and arise
from the need for a dynamic balance between positive and negative feedback. 相似文献
11.
Pierre-Alain Monnard H.-J. Ziock 《Origins of life and evolution of the biosphere》2007,37(4-5):469-472
The construction of artificial cells or protocells that are a simplified version of contemporary cells will have implications
for both the understanding of the origins of cellular Life and the design of “cell-like” chemical factories. In this short
communication, we discuss the progress and remaining issues related to the construction of protocells from metabolic products.
We further outline the de novo design of a simple chemical system that mimics the functional properties of a living cell without
being composed of molecules of biological origin, thereby addressing issues related to Life’s origins.
Presented at: International School of Complexity—4th Course: Basic Questions on the Origins of Life; “Ettore Majorana” Foundation
and Centre for Scientific Culture, Erice, Italy, 1–6 October 2006. 相似文献
12.
H. R. van der Vaart 《Bulletin of mathematical biology》1973,35(1-2):195-211
Many mathematical models for physical and biological problems have been and will be built in the form of differential equations
or systems of such equations. With the advent of digital computers one has been able to find (approximate) solutions for equations
that used to be intractable. Many of the mathematical techniques used in this area amount to replacing the given differential
equations by appropriate difference equations, so that extensive research has been done into how to choose appropriate difference
equations whose solutions are “good” approximations to the solutions of the given differential equations.
The present paper investigates a different, although related problem. For many physical and biological phenomena the “continuum”
type of thinking, that is at the basis of any differential equation, is not natural to the phenomenon, but rather constitutes
an approximation to a basically discrete situation: in much work of this type the “infinitesimal step lengths” handled in
the reasoning which leads up to the differential equation, are not really thought of as infinitesimally small, but as finite;
yet, in the last stage of such reasoning, where the differential equation rises from the differentials, these “infinitesimal”
step lengths are allowed to go to zero: that is where the above-mentioned approximation comes in. Under this kind of circumstances,
it seems more natural tobuild themodel as adiscrete difference equation (recurrence relation) from the start, without going through the painful, doubly approximative process
of first, during the modeling stage, finding a differential equation to approximate a basically discrete situation, and then,
for numerical computing purposes, approximating that differential equation by a difference scheme.
The paper pursues this idea for some simple examples, where the old differential equation, though approximative in principle,
had been at least qualitatively successful in describing certain phenomena, and shows that this idea, though plausible and
sound in itself, does encounter some difficulties. The reason is that each differential equation, as it is set up in the way
familiar to theoretical physicists and biologists, does correspond to a plethora of discrete difference equations, all of
which in the limit (as step length→0) yield the same differential equation, but whose solutions, for not too small step length,
are often widely different, some of them being quite irregular. The disturbing thing is that all these difference equations
seem to adequately represent the same (physical or biological) reasoning as the differential equation in question. So, in
order to choose the “right” difference equation, one may need to draw upon more detailed (physical or) biological considerations.
All this does not say that one should not prefer discrete models for phenomena that seem to call for them; but only that their
pursuit may require additional (physical or) biological refinement and insight.
The paper also investigates some mathematical problems related to the fact of many difference equations being associated with
one differential equation. 相似文献
13.
This study is related to a model describing the behavior of barium-treatedAplysia neurons generating regular burst-plateau patterns. The model is represented by an autonomous dynamical system, defined inR
4 and depending on a small parameter. This paper is restricted to the qualitative study of three “reduced systems” deduced
from the “complete system”. Part of the study is performed with the use of the qualitative theory of singular perturbations.
The predicted behaviors are compared with experimental results. 相似文献
14.
I. Opatowski 《Bulletin of mathematical biology》1946,8(3):101-119
The calculation of the size of the “sensitive volume” or “control center” in biological effects of radiations is discussed
from the viewpoint of the probabilistic theory of these phenomena based on the concept of random “effective events”. On the
bases of that theory, the resistivity of a microorganism to radiation is defined as its “mean life” under a radiation of one
roentgen per minute. This mean is calculated for processes with and without recovery. The case of variable sensitivity, as
it occurs for instance during mitosis, is discussed in detail. Methods are given to calculate this variability from survival
curves or similar experimental data. The theory is applied to experiments of A. Zuppinger on irradiation ofAscaris eggs with X-rays. 相似文献
15.
Populations of the Chalcolithic Levant as defined by archaeological excavations has in many cases reinforced the traditional
scheme that a number of “races” are present. This scheme is usually based not only on differential cultural traditions as
identified by archeologists, but also on the available skeletal evidence as discussed by physical anthropologists. Recently
this view has been challenged and it has been suggested that the metrical and anatomical range of variability as identified
within Chalcolithic populations can be subsumed into a single population or “racial” range. This paper examines both the available
biological and archaeological evidence from the Chalcolithic Levant and concludes that there is no strong archaeological or
biological evidence to support a multiple “racial” origin for the Chalcolithic of the Levant. 相似文献
16.
N. Rashevsky 《Bulletin of mathematical biology》1962,24(3):327-334
Following the program outlined in a previous paper (Bull. Math. Biophysics,23, 237–260, 1961), a further abstract study is made of some simple relational systems which possess some properties of living
organisms. It is shown that the “one gene-one enzyme” hypothesis leads to the conclusion that either all genes are built of
the same chemical building blocks, or that at least all genes have a number of building blocks in common. A consistent relational
application of the “one gene-one enzyme” hypothesis leads moreover to the conclusion that replication is not an inherent property
of a gene. Rather there must be a set of enzymes which “copy” the genes. The number of enzymes in this set must be less than
the number of genes and therefore the activity of those “copying” enzymes cannot be absolutely specific. 相似文献
17.
In view of the increasing evidence that multicomponent diffusion effects could be significant in biological gas exchange systems,
a non-equimolar film model of multicomponent diffusion was derived. “Osmotic” ternary diffusion was studied for the gas systems
He−N2−O2, He−SF6−O2, and N2−SF6−O2. Diffusional fluxes and concentration profiles were calculated under both the “square-root” and the “product” flux conditions.
Results were also compared with those obtained using the equimolar flux condition. It was found that the greater the difference
of the diffusibilities between the two active components in a system, the greater the osmotic fluxes, and also the more alinear
the concentration profiles. These results support the suggestion that the “product” condition applies to molecular diffusion
in free space, the “square-root” condition to molecular diffusion in pores, and the equimolar flux condition to closed diffusion
systems. 相似文献
18.
Anthony F. Bartholomay 《Bulletin of mathematical biology》1958,20(3):175-190
A stochastic model for the basic unimolecular chemical reaction
is derived. This model provides a mathematical basis, altogether missing in the current kinetic theory, for the analysis
of inherent random fluctuations about the strict concentration-time course prescribed by the existing deterministic theory.
Limits on the extent of the predicted inherent variability are obtained and compared with those usually expected purely on
the basis of random experimental errors of extraneous origin (not associated with the mechanism of reaction). The results
support the extrapolation to chemical systems of a principle of statistical inaccuracy for physical systems which has been
called by E. Schroedinger “the
Law of Physics.” 相似文献
19.
A seaweed with the local name “endong” is a rare eucheumoid variety that has recently been farmed in Tawi-Tawi, southern Philippines.
Local farmers describe it as “eel-like” because of its long, slender and smooth thalli. Being somewhat similar in appearance
to the dominantly farmed seaweed “tambalang” (Kappaphycus alvarezii var. tambalangii), farmers mix their harvests of “endong” with those of “tambalang”. We analyzed the hydrocolloid extract from “endong” using
spectroscopic and chemical techniques. The extract’s infrared and nuclear magnetic resonance (1H and 13C) spectra, and sulfate and 3,6-anhydrogalactose contents revealed carrageenan of the iota-type, similar to extracts from
another farmed species, Eucheuma denticulatum. This result implies that “endong” carrageenan exhibits physico-chemical properties different from those of kappa-carrageenan
of “tambalang”. The findings of this study are of significance to the seaweed industry, as carrageenan quality problems could
potentially arise from a mixed harvest. Seaweed farmers are advised to separate their harvests of “endong” and “tambalang”.
Presented at the 19th International Seaweed Symposium, Kobe, Japan 相似文献
20.
This article proposes an abstract mathematical frame for describing some features of cognitive and biological time. We focus
here on the so called “extended present” as a result of protentional and retentional activities (memory and anticipation).
Memory, as retention, is treated in some physical theories (relaxation phenomena, which will inspire our approach), while
protention (or anticipation) seems outside the scope of physics. We then suggest a simple functional representation of biological
protention. This allows us to introduce the abstract notion of “biological inertia”. 相似文献