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1.
Francesco Andrietti 《Bulletin of mathematical biology》1978,40(6):839-851
An analysis of the interactions among asymptotically stable dynamical systems is formulated by making use of the dynamical
system theory. Some results coming from previous mathematical analyses have been slightly modified to take into account some
typical biological constraints as the boundedness properties of the solutions. In particular it has been shown that when the
“coupling” among the subsystems is “loose” enough (in a sense that has to be made mathematically precise) the asymptotic behaviour
of a complex system is the same of that of its individual components. The mathematical theory has been used to analyze two
systems of biological significance: the coupling among chemical reactions and the stability properties of a 4-dimensional
system describing the kinetics of a chemical transmitter. 相似文献
2.
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
3.
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
4.
The Center for Biologics Evaluation and Research, whose regulatory authority includes monoclonal antibodies, cytokines, vaccines,
toxins and somatic cellular therapies, communicates to sponsors issues for consideration in the development of biological
products through the publication of “Points to Consider” and “Guideline” documents. This paper summarizes the available “Points
to Consider” and “Guideline” documents and outlines recommendations from these documents for characterizing the cells used
to produce biological products. 相似文献
5.
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
6.
Guillermo A. Logarzo Eduardo G. Virla Erica Luft Albarracin Serguei V. Triapitsyn Walker A. Jones Jesse H. de León Juan A. Briano 《BioControl》2012,57(1):37-48
The South American egg parasitoid Gonatocerus sp. near tuberculifemur “Clade 1” (G. sp. “Clade 1”) (Hymenoptera: Mymaridae) is a new association of the glassy-winged sharpshooter (GWSS), Homalodisca
vitripennis (Germar) (Cicadellidae) and a candidate for its biological control in California, USA. In Argentina, G. sp. “Clade 1” was screened in the laboratory (no-choice tests) and in the field (multiple choice tests) against eggs of 32
Auchenorrhyncha host species and other four potential hosts unrelated to sharpshooters. In no-choice assays, it parasitized
only eggs within the leafhopper tribe Proconiini. In contrast, in the long term field tests, it emerged not only from eggs
of the Proconiini but also from two species of Cicadellini at low numbers (five wasps out of 698 exposed eggs). Two interpretations
arise from the results: (1) Host associations of G. sp. “Clade 1” are restricted to the Proconiini whereas field parasitization of the Cicadellini species were false positive,
or (2) G. sp. “Clade 1” parasitizes also some Cicadellini species and its rejection in the laboratory was a false negative. Both interpretations
are discussed. Insect motivation could be the explanation for the negative results in the no-choice tests. On the other hand,
in the more natural field situations, the host selection process and oviposition behavior should not have been affected and
host range would be more realistic. The parasitism of the Cicadellini species would be indicative of a potential non-target
effect on the sharpshooters in the USA. 相似文献
7.
Sarah S. Richardson 《Biology & philosophy》2010,25(5):823-841
This paper describes, analyzes, and critiques the construction of separate “male” and “female” genomes in current human genome
research. Comparative genomic work on human sex differences conceives of the sexes as like different species, with different
genomes. I argue that this construct is empirically unsound, distortive to research, and ethically questionable. I propose
a conceptual model of biological sex that clarifies the distinction between species and sexes as genetic classes. The dynamic
interdependence of the sexes makes them “dyadic kinds” that are not like species, which are “individual kinds.” The concept
of sex as a “dyadic kind” may be fruitful as a remedy to the tendency to conceive of the sexes as distinct, binary classes
in biological research on sex more generally. 相似文献
8.
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
9.
Promoters of the PhyloCode have mounted an intensive and deceptive publicity campaign. At the centerpiece of this campaign
have been slogans such as that the Linnaean System will “goof you up,” that the PhyloCode is the “greatest thing since sliced
bread,” and that systematists are “afraid” to propose new names because of “downstream consequences.” Aside from such subscientific
spin and sloganeering, proponents of the PhyloCode have offered nothing real to back up claims of greater stability for their
new system. They have also misled many into believing that the PhyloCode is the only truly phylogenetic system. The confusion
that has been fostered involves several discrete arguments, concerning: a new “method” of “designating” names, rank-free taxonomy,
uninomial nomenclature, and issues of priority. Claims that the PhyloCode produces a more stable nomenclature are false, as
shown with the example of “paleoherbs.” A rank-free system of naming requires an annotated reference tree for even the simplest
exchanges of information. This would be confusing at best and would cripple our ability to teach, learn, and use taxonomic
names in the field or in publications. We would be confronted by a mass of polynomial names, tied together only by a tree
graphic, with no agreed name (except a uninomial, conveying no hierarchy) to use for any particular species. The separate
issue of stability in reference to rules of priority and rank can be easily addressed within the current codes, by implementation
of some simple changes, as we will propose in this article. Thus there is no need to “scrap” the current Linnaean codes for
a poorly reasoned, logically inconsistent, and fatally flawed new code that will only bring chaos. 相似文献
10.
Nathalie Gontier 《Evolution》2011,4(3):515-538
It is a popularly held view that Darwin was the first author to draw a phylogenetic tree diagram. However, as is the case
with most popular beliefs, this one also does not hold true. Firstly, Darwin never called his diagram of common descent a
tree. Secondly, even before Darwin, tree diagrams were used by a variety of philosophical, religious, and secular scholars
to depict phenomena such as “logical relationships,” “affiliations,” “genealogical descent,” “affinity,” and “historical relatedness”
between the elements portrayed on the tree. Moreover, historically, tree diagrams themselves can be grouped into a larger
class of diagrams that were drawn to depict natural and/or divine order in the world. In this paper, we trace the historical
roots and cultural meanings of these tree diagrams. It will be demonstrated that tree diagrams as we know them are the outgrowth
of ancient philosophical attempts to find the “true order” of the world, and to map the world “as it is” (ontologically),
according to its true essence. This philosophical idea would begin a fascinating journey throughout Western European history.
It lies at the foundation of the famous “scala naturae,” as well as religious and secular genealogical thinking, especially
in regard to divine, familial (kinship), and linguistic pedigrees that were often depicted by tree images. These scala naturae
would fuse with genealogical, pedigree thinking, and the trees that were the result of this blend would, from the nineteenth
century onward, also include the element of time. The recognition of time would eventually lead to the recognition of evolution
as a fact of nature, and subsequently, tree iconographies would come to represent exclusively the evolutionary descent of
species. 相似文献
11.
Protein evolution is not a random process. Views which attribute randomness to molecular change, deleterious nature to single-gene
mutations, insufficient geological time, or population size for molecular improvements to occur, or invoke “design creationism”
to account for complexity in molecular structures and biological processes, are unfounded. Scientific evidence suggests that
natural selection tinkers with molecular improvements by retaining adaptive peptide sequence. We used slot-machine probabilities
and ion channels to show biological directionality on molecular change. Because ion channels reside in the lipid bilayer of
cell membranes, their residue location must be in balance with the membrane’s hydrophobic/philic nature; a selective “pore”
for ion passage is located within the hydrophobic region. We contrasted the random generation of DNA sequence for KcsA, a
bacterial two-transmembrane-domain (2TM) potassium channel, from Streptomyces lividans, with an under-selection scenario, the “jackprot,” which predicted much faster evolution than by chance. We wrote a computer
program in JAVA APPLET version 1.0 and designed an online interface, The Jackprot Simulation
, to model a numerical interaction between mutation rate and natural selection during a scenario of polypeptide evolution.
Winning the “jackprot,” or highest-fitness complete-peptide sequence, required cumulative smaller “wins” (rewarded by selection)
at the first, second, and third positions in each of the 161 KcsA codons (“jackdons” that led to “jackacids” that led to the
“jackprot”). The “jackprot” is a didactic tool to demonstrate how mutation rate coupled with natural selection suffices to
explain the evolution of specialized proteins, such as the complex six-transmembrane (6TM) domain potassium, sodium, or calcium
channels. Ancestral DNA sequences coding for 2TM-like proteins underwent nucleotide “edition” and gene duplications to generate
the 6TMs. Ion channels are essential to the physiology of neurons, ganglia, and brains, and were crucial to the evolutionary
advent of consciousness. The Jackprot Simulation illustrates in a computer model that evolution is not and cannot be a random
process as conceived by design creationists. 相似文献
12.
Microrheological properties (aggregation and deformability) of erythrocytes separated by centrifugation at 30000×g density gradient into “young” and “old” (the upper and lower fractions, respectively) were studied. The erythrocytes were
taken from physically active persons (PAP) and from those with elevated arterial pressure (EAP). A significant difference
in microrheological properties of the “young” and “old” erythrocytes was found. The aggregation degree of “old” cells was
nearly twice that of “young” cells. The deformability of the erythrocyte subpopulations was significantly different, though
the difference was not so pronounced as in the case of aggregation. The aggregation of “young” and “old” erythrocytes in the
PAP group was the least (28% lower than in the control). Note, that “old” erythrocytes in the PAP group had better microrheological
properties than in the other groups. All erythrocyte populations in the EAP group were characterized by higher aggregation,
decreased deformability, and decreased capacity for oxygen transport. 相似文献
13.
We propose a simple experiment to study delocalization and extinction in inhomogeneous biological systems. The nonlinear
steady state for, say, a bacteria colony living on and near a patch of nutrient or favorable illumination (“oasis”) in the
presence of a drift term (“wind”) is computed. The bacteria, described by a simple generalization of the Fisher equation,
diffuse, divide A→A + A, die A→ 0, and annihilate A + A→ 0. At high wind velocities all bacteria are blown into an unfavorable region (“desert”), and the colony dies out. At low
velocity a steady state concentration survives near the oasis. In between these two regimes there is a critical velocity at
which bacteria first survive. If the “desert” supports a small nonzero population, this extinction transition is replaced
by a delocalization transition with increasing velocity. Predictions for the behavior as a function of wind velocity are made
for one and two dimensions.
Received: 3 August 1998 / Revised version: 17 July 1999 / Published online: 4 July 2000 相似文献
14.
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
15.
This paper presents a number of deterministic models for theoretically assessing the potential impact of an imperfect prophylactic HIV-1 vaccine that has five biological modes of action, namely “take,” “degree,” “duration,” “infectiousness,” and “progression,” and can lead to increased risky behavior. The models, which are of the form of systems of nonlinear differential equations, are constructed via a progressive refinement of a basic model to incorporate more realistic features of HIV pathogenesis and epidemiology such as staged progression, differential infectivity, and HIV transmission by AIDS patients. The models are analyzed to gain insights into the qualitative features of the associated equilibria. This allows the determination of important epidemiological thresholds such as the basic reproduction numbers and a measure for vaccine impact or efficacy. The key findings of the study include the following (i) if the vaccinated reproduction number is greater than unity, each of the models considered has a locally unstable disease-free equilibrium and a unique endemic equilibrium; (ii) owing to the vaccine-induced backward bifurcation in these models, the classical epidemiological requirement of vaccinated reproduction number being less than unity does not guarantee disease elimination in these models; (iii) an imperfect vaccine will reduce HIV prevalence and mortality if the reproduction number for a wholly vaccinated population is less than the corresponding reproduction number in the absence of vaccination; (iv) the expressions for the vaccine characteristics of the refined models take the same general structure as those of the basic model. 相似文献
16.
Keith Johnson 《Journal of biological physics》2012,38(1):85-95
Water nanoclusters are shown from first-principles calculations to possess unique terahertz-frequency vibrational modes in
the 1–6 THz range, corresponding to O–O–O “bending,” “squashing,” and “twisting” “surface” distortions of the clusters. The
cluster molecular-orbital LUMOs are huge Rydberg-like “S,” “P,” “D,” and “F” orbitals that accept an extra electron via optical
excitation, ionization, or electron donation from interacting biomolecules. Dynamic Jahn–Teller coupling of these “hydrated-electron”
orbitals to the THz vibrations promotes such water clusters as vibronically active “structured water” essential to biomolecular
function such as protein folding. In biological microtubules, confined water-cluster THz vibrations may induce their “quantum
coherence” communicated by Jahn–Teller phonons via coupling of the THz electromagnetic field to the water clusters’ large
electric dipole moments. 相似文献
17.
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
18.
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
19.
Numerous biological interactions, such as interactions between T cell receptors or antibodies with antigens, interactions
between enzymes and substrates, or interactions between predators and prey are often not strictly specific. In such less specific,
or “sloppy,” systems, referred to here as degenerate systems, a given unit of a diverse resource (antigens, enzymatic substrates,
prey) is at risk of being recognized and consumed by multiple consumers (lymphocytes, enzymes, predators). In this study,
we model generalized degenerate consumer-resource systems of Lotka–Volterra and Verhulst types. In the degenerate systems
of Lotka–Volterra, there is a continuum of types of consumer and resource based on variation of a single trait (characteristic,
or preference). The consumers experience competition for a continuum of resource types. This non-local interaction system
is modeled with partial differential-integral equations and shows spontaneous self-structuring of the consumer population
that depends on the degree of interaction degeneracy between resource and consumer, but does not mirror the distribution of
resource. We also show that the classical Verhulst (i.e. logistic) single population model can be generalized to a degenerate
model, which shows qualitative behavior similar to that in the degenerate Lotka–Volterra model. These results provide better
insight into the dynamics of selective systems in biology, suggesting that adaptation of degenerate repertoires is not a simple
“mirroring” of the environment by the “fittest” elements of population. 相似文献
20.
Miles B. Markus 《Journal of the history of biology》2011,44(4):781-786
The term “hypnozoite” is derived from the Greek words hypnos (sleep) and zoon (animal). Hypnozoites are dormant forms in the life cycles of certain parasitic protozoa that belong to the Phylum Apicomplexa
(Sporozoa) and are best known for their probable association with latency and relapse in human malarial infections caused
by Plasmodium ovale and P. vivax. Consequently, the hypnozoite is of great biological and medical significance. This, in turn, makes the origin of the name
“hypnozoite” a subject of interest. Some “missing” history that is now placed on record (including a letter written by P.
C. C. Garnham, FRS) shows that Miles B. Markus coined the term “hypnozoite”. While a PhD student at Imperial College London,
he carried out research that led to the identification of an apparently dormant form of Cystoisospora (synonym: Isospora). In 1976, he speculated: “If sporozoites of Isospora can behave in this fashion, then those of related Sporozoa, like malaria parasites, may have the ability to survive in the
tissues in a similar way.” He adopted the term “hypnozoite” for malaria in 1978 when he wrote in a little-known journal that
this name would “… describe any dormant sporozoites or dormant, sporozoite-like stages in the life cycles of Plasmodium or other Haemosporina.” At that time, the existence of a hypnozoite form in the life cycle of Plasmodium was still a hypothetical notion. In 1980, however, Wojciech A. Krotoski published (together with several co-workers) details
concerning his actual discovery of malarial hypnozoites, an event of considerable importance. 相似文献