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1.
Fitts’ law is a well established empirical formula, known for encapsulating the “speed-accuracy trade-off”. For discrete,
manual movements from a starting location to a target, Fitts’ law relates movement duration to the distance moved and target
size. The widespread empirical success of the formula is suggestive of underlying principles of human movement control. There
have been previous attempts to relate Fitts’ law to engineering-type control hypotheses and it has been shown that the law
is exactly consistent with the closed-loop step-response of a time-delayed, first-order system. Assuming only the operation
of closed-loop feedback, either continuous or intermittent, this paper asks whether such feedback should be predictive or
not predictive to be consistent with Fitts law. Since Fitts’ law is equivalent to a time delay separated from a first-order
system, known control theory implies that the controller must be predictive. A predictive controller moves the time-delay
outside the feedback loop such that the closed-loop response can be separated into a time delay and rational function whereas
a non- predictive controller retains a state delay within feedback loop which is not consistent with Fitts’ law. Using sufficient
parameters, a high-order non-predictive controller could approximately reproduce Fitts’ law. However, such high-order, “non-parametric”
controllers are essentially empirical in nature, without physical meaning, and therefore are conceptually inferior to the
predictive controller. It is a new insight that using closed-loop feedback, prediction is required to physically explain Fitts’
law. The implication is that prediction is an inherent part of the “speed-accuracy trade-off”. 相似文献
2.
The dynamic response of human musculo-skeletal framework is treated by (i) idealization of the musculo-skeletal framework
as hybrid structural networks possessing feedback characteristics and then (ii) employing linegraph-flowgraph procedures for
the feedback characterization of the hybrid structural networks. Topological procedures are used in which a “tree” of a network
furnishes the skeleton upon which the “linkage” (muscle representing) members provide interaction. Feedback characterization
(representing the sensitivity of the skeletal members to the tensile forces) is defined, between the internal “linkage” and
“tree” members, by means of the flowgraph. Mikusinski operational calculus is used to facilitate representation of inertia
effects by dynamic feedback characterization, with inclusion of initial conditions. 相似文献
3.
Anatol Rapoport 《Bulletin of mathematical biology》1961,23(4):321-335
As a “base line” of memorization performance, the behavior of a “perfect learner” is considered. He is characterized by a
perfect memory and by the ability to choose the best search procedure in problems where the correct response from a given
repertoire is to be found to each of several stimuli under the condition of “right” and “wroing” promptings by the experimenter.
Expected learning curves are derived for the case of disjoint response repertoires associated with the stimuli under cyclic
and random presentation of the stimuli and for the case of a single response repertoire (a one-to-one matching problem) under
cyclic presentation. 相似文献
4.
Dionyssis Venieratos 《Bulletin of mathematical biology》1981,43(2):213-232
Two simple models are proposed and analysed, in which it is shown that the formation of a new polymer, resulting from an “error”
in the template action mechanism of production of an old polymer, may compromise the stability of the initial system under
specific conditions, in the context of prebiotic evolution. Autocatalysis is shown to be a “selective advantage”, enabling
the “mutant” to dominate in concentration and even replace the initial polymer. The addition of a third molecule playing the
role of a catalyst causes hysteresis effects. 相似文献
5.
John Miles Little 《Journal of bioethical inquiry》2010,7(1):91-102
Aesthetics is a vexed topic in philosophy, with a long history. For my purposes, an aesthetic experience is a foundational
affective response to an object, to which terms such as “ugly”, “beautiful”, “pretty” or “harmonious” are applied. These terms
are derived from a Discourse of aesthetics; some remain constant, others change from generation to generation. Aesthetics
and ethics have been linked in Western thought since the days of Plato and Aristotle. This essay examines what is happening
to that link in contemporary experience. It emphasises the ways in which the popular media exploit aesthetic appeal to penetrate
their market, and to exploit and frame intuitive responses to current and past events. Production values, the artfulness of
editors and the financial interests of producers and directors thus do much to determine contemporary aesthetic and ethical
judgements. That which is beautifully presented invites the ethical involvement of the audience. Events whose images are beautifully
presented constitute “hyperevidence”, a pre-judged, reinforced and amplified illusion of reality and participation. Understanding
how aesthetic excellence draws audiences into ethical relationship with what is presented becomes an important part of education
in ethics, including bioethics. 相似文献
6.
Willson SJ 《Bulletin of mathematical biology》2007,69(8):2561-2590
Suppose G is a phylogenetic network given as a rooted acyclic directed graph. Let X be a subset of the vertex set containing the root, all leaves, and all vertices of outdegree 1. A vertex is “regular” if
it has a unique parent, and “hybrid” if it has two parents. Consider the case where each gene is binary. Assume an idealized
system of inheritance in which no homoplasies occur at regular vertices, but homoplasies can occur at hybrid vertices. Under
our model, the distances between taxa are shown to be described using a system of numbers called “originating weights” and
“homoplasy weights.” Assume that the distances are known between all members of X. Sufficient conditions are given such that the graph G and all the originating and homoplasy weights can be reconstructed from the given distances. 相似文献
7.
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
8.
N
eoturris breviconis (Anthomedusae) has a nerve plexus in the walls of its endodermal canals. The plexus is distinct from the ectodermal nerve
plexuses supplying the radial and circular muscles in the ectoderm and no connections have been observed between them. Stimulation
of the endodermal plexus evokes electrical events recorded extracellularly as “E” potentials. These propagate through all
areas where the plexus has been shown by immunohistology to exist and nowhere else. When Neoturris is ingesting food, trains of “E” potentials propagate down the radial canals to the margin and cause inhibition of swimming.
This response is distinct from the inhibition of swimming associated with contractions of the radial muscles but both may
play a part in feeding and involve chemoreceptors. Preliminary observations suggest that the “E” system occurs in other medusae
including Aglantha digitale (Trachymedusae) where the conduction pathway was previously thought to be an excitable epithelium. 相似文献
9.
Mathematical models of mutually interacting reverberatory neural circuits exhibit decision-making properties that can account
for behavioral mode selection in terms of identifiable neural subsystems and measurable variables, without the need for invoking
concepts such as “drive,” “motivation,” or “instinct”. The models can account for an animal's ability to persist in a given
behavioral mode under appropriate stimulus conditions and to rapidly switch modes in response to significant stimulus changes
via the properties of stable steady states, thresholds for steady-state transitions, and the lack of intrinsic oscillations. 相似文献
10.
Alvin M. Weinberg 《Bulletin of mathematical biology》1942,4(1):33-44
The standard two factor excitation theories should be called “preexcitation” theories since they apply only to those events
occurring just up to excitation. A true phenomenological excitation theory which describes thewhole excitation cycle must involve non-linear equations. The nature of these non-linearities is suggested by B. Katz's subthreshold
response data. From this data is constructed a “local phenomenological characteristic” which is analogous to the current-voltage
characteristic of a non-linear electrical or mechanical system capable of displaying relaxation oscillations. Excitation by
constant currents is shown to occur where the slope of the characteristic changes sign. The variation of the time constant
of excitation with degree of response, explained by W. A. H. Rushton in terms of a liminal length, is described here in purely
formal terms. The theory as presented explicity treats only those events in the excitation cycle up to and a little beyond
excitation; the complete excitation cycle (including recovery and repetition) is mentioned as being amenable to mathematical
treatment by an extension of the present theory. 相似文献
11.
N. Rashevsky 《Bulletin of mathematical biology》1947,9(1):1-8
We may consider that most of the human behavior is a set of learned responses to certain patterns which recur frequently in
the course of human life. Some “abnormal” events or experiences may result in the learning of abnormal responses, and thus
in abnormal behavior. The “abnormal” responses may begin to be learned after some of the normal response patterns have been
fairly well established. The development of both normal and abnormal behavior may thus be represented by learning curves of
the type studied by H. D. Landahl. Applying some of the results of the theory of learning curves and considering that the
normal and abnormal reactions may reciprocally inhibit each other, a quantitative theory of some psychoses may be developed.
In particular, the effects of shock may be deduced from the assumption that they cause the more recently learned abnormal
reactions to be “unlearned” more readily, than the earlier learned “normal” reactions. The effectiveness of shock treatments
as a function of the duraction of psychosis is discussed from this point of view. 相似文献
12.
Victoria N. Alexander 《Biosemiotics》2009,2(1):77-100
Hackles have been raised in biosemiotic circles by T. L. Short’s assertion that semiosis, as defined by Peirce, entails “acting
for purposes” and therefore is not found below the level of the organism (2007a:174–177). This paper examines Short’s teleology and theory of purposeful behavior and offers a remedy to the disagreement.
Remediation becomes possible when the issue is reframed in the terms of the complexity sciences, which allows intentionality
to be understood as the interplay between local and global aspects of a system within a system. What is called “acting for
purposes” is not itself a type of behavior so much as a relationship between a dynamic system that “exists for a purpose”
and its microprocesses that “serve purposes.” The “intentional object” of philosophy is recast here as the holistic self-organized
dynamics of a system, which exists for the purpose of self-maintenance, and that constrains the parts’ behaviors, which serve
the purpose of forming the system. (A “system” can be any emergent, e.g. an abiotic form, an adapted species, a self, a conditioned response, thought, or a set of ideas.) The self-organized whole,
which is represented to the parts in their own constrained behaviors, assumes the guiding function so long attributed to the
mysterious “intentional object.” If emergent self-causation is not disallowed, creative originality, as well as directionality, becomes part of the definition of purposeful behavior. Thus, key tools used here, required for understanding emergence, come
from poetics rather than semoitics. In the microprocesses of self-organization, I find what I call “accidental” indices and
icons — which are poetic in the sense that they involve mere metonymic contiguity and metaphoric similarity — and which are
preferentially selected under constrained conditions allowing radically new connections to habituate into an “intentional”
self-organized system that, not coincidentally, has some of the emergent characteristics of a conventional symbolic system.
相似文献
Victoria N. AlexanderEmail: |
13.
Nils Roll-Hansen 《Biology & philosophy》1989,4(3):303-329
I call an experiment “crucial” when it makes possible a decisive choice between conflicting hypotheses. Joharmsen's selection
for size and weight within pure lines of beans played a central role in the controversy over continuity or discontinuity in
hereditary change, often known as the Biometrician-Mendelian controversy. The “crucial” effect of this experiment was not
an instantaneous event, but an extended process of repeating similar experiments and discussing possible objections. It took
years before Johannsen's claim about the genetic stability of pure lines was accepted as conclusively demonstrated by the
community of geneticists.
The paper also argues that crucial experiments thus interpreted contradict certain ideas about the underdetermination of theories
by facts and the theory-ladenness of facts which have been influential in recent history and sociology of science. The acceptance
of stability in the pure lines did not rest on prior preference for continuity or discontinuity. And this fact permitted a
final choice between the two theories. When such choice is characterized as “decisive” or “final”, this is not meant in an
absolute philosophical sense. What we achive in these cases is highly reliable empirical knowledge. The philosophical possibility
of drawing (almost) any conclusion in doubt should be distinguished from reasonable doubt in empirical science. 相似文献
14.
B. B. Kheyfets S. I. Mukhin 《Biochemistry (Moscow) Supplemental Series A: Membrane and Cell Biology》2011,5(4):392-399
Two-phase lipid membrane is modeled with lipids of different bending rigidity of hydrophobic tails: domains consist of “rigid”
lipid liquid condensed phase and are surrounded by the “flexible” lipid liquid expanded phase. Within the framework of the
earlier proposed model of flexible strings, entropic contribution not including mismatch energy is calculated analytically.
“Entropic” line tension is found to be weakly dependent on the domain radius. According to the model, it is shown that merely
“entropic mismatch” is not enough for the domain formation. In the paper it is assumed that lipids at the boundary, on the
average, have larger area than the ones in the volume. This leads to an increase of energy of boundary lipids. Cases of lipids
with nearly the same bending rigidities and with strongly different ones are considered. Free energy is calculated using Taylor
expansion on the difference of area of lipids at the domain’s boundary and in the volume. Based on the calculated boundary
energy domain stability in the finite system is estimated. 相似文献
15.
Hidden treatments in ecological experiments: re-evaluating the ecosystem function of biodiversity 总被引:68,自引:0,他引:68
Michael A. Huston 《Oecologia》1997,110(4):449-460
Interactions between biotic and abiotic processes complicate the design and interpretation of ecological experiments. Separating
causality from simple correlation requires distinguishing among experimental treatments, experimental responses, and the many
processes and properties that are correlated with either the treatments or the responses, or both. When an experimental manipulation
has multiple components, but only one of them is identified as the experimental treatment, erroneous conclusions about cause
and effect relationships are likely because the actual cause of any observed response may be ignored in the interpretation
of the experimental results. This unrecognized cause of an observed response can be considered a “hidden treatment.” Three
types of hidden treatments are potential problems in biodiversity experiments: (1) abiotic conditions, such as resource levels,
or biotic conditions, such as predation, which are intentionally or unintentionally altered in order to create differences
in species numbers for “diversity” treatments; (2) non-random selection of species with particular attributes that produce
treatment differences that exceed those due to “diversity” alone; and (3) the increased statistical probability of including
a species with a dominant negative or positive effect (e.g., dense shade, or nitrogen fixation) in randomly selected groups
of species of increasing number or “diversity.” In each of these cases, treatment responses that are actually the result of
the “hidden treatment” may be inadvertently attributed to variation in species diversity. Case studies re-evaluating three
different types of biodiversity experiments demonstrate that the increases found in such ecosystem properties as productivity,
nutrient use efficiency, and stability (all of which were attributed to higher levels of species diversity) were actually
caused by “hidden treatments” that altered plant biomass and productivity.
Received: 16 December 1996 / Accepted: 2 March 1997 相似文献
16.
I. N. Konareva 《Neurophysiology》2006,38(3):201-208
Modifications of different EEG rhythms induced by a single neurofeedback session (by the EEG characteristics) directed toward
an increase in the ratio of the spectral powers (SPs) of the α vs θ oscillations were compared with the psychological characteristics of the tested subjects (the group included 30 persons).
A generally accepted neurofeedback technique was used; the intensity of acoustic white noise served as the feedback signal.
EEG potentials were recorded from the C3 and C4 leads. Psychological testing was carried out using Eysenck’s (EPQ), Rusalov’s
(OST), and (16 PF) questionnaires. The directions of changes in the SPs of EEG frequency components were found to significantly
correlate with some individuality-related peculiarities of the tested subjects. The SP of the δ rhythm correlated with the
EPQ scale “neuroticism,” OST scale “social plasticity,” and 16 PF factors H (“parmia”), I (“premsia”), and Q3 (“self-control of behavior”). The SP of the θ component demonstrated correlations with the OST scales “ergisity,” “plasticity,”
and “social temp” and with 16 PF factors M (“autia”), Q4 (“frustration”), and Q1 (“exvia”). The SP of the α rhythm correlated with 16 PF factors Q3 (“self-control of behavior”), G (“strength of superEgo”), O (“hypothymia”), L (“protension”), and N (“shrewdness”). The SP
of the β rhythm correlated with the OST scale “emotionality,” while that of the γ rhythm showed correlations with the 16 PF
indices L (“protension”) and M (“autia”). Changes in the ratio of the α vs θ SPs correlated with the EPQ scale “neuroticism.” Thus, our data confirm the statement that a high individual variability
of the results of a single (first in the series) neurofeedback session is to a great extent related to peculiarities of the
individual psychological pattern of the subject.
Neirofiziologiya/Neurophysiology, Vol. 38, No. 3, pp. 239–247, May–June, 2006. 相似文献
17.
This article attempts to convey the joys and frustrations of skimming the Internet trying to find relevant information concerning
an academic’s work as a scientist, a student or an instructor. A brief overview of the Internet and the “do’s and don’ts”
for the neophyte as well for the more seasoned “navigator” are given. Some guidelines of “what works and what does not” and
“what is out there” are provided for the scientist with specific emphasis for biologists, as well as for all others having
an interest in science but with little interest in spending countless hours “surfing the net”. An extensive but not exhaustive
list of related websites is provided. 相似文献
18.
T. C. R. White 《Ecological Research》2007,22(2):354-357
Many recent ecological studies have demonstrated that animal populations are limited by their food. Examples are presented
here to refute the view that natural populations are regulated by negative feedback mortality factors. Additionally, several
incorrect statements in a recent publication are discussed, specifically (1) that there is no difference between the concepts
of regulation and limitation; (2) that the debate is about what causes the time it takes a population to reach the carrying
capacity of its habitat, not what sets that carrying capacity; (3) that the results of a laboratory experiment using a closed
population with fixed amounts of food represents what happens in natural open populations with varying supplies of food; (4)
that a thermostat analogy can be used, assuming that an “equilibrium” is controlling natural populations “from above” instead
of the original steam analogy which says the varying input of a resource “from below” is the controlling factor. 相似文献
19.
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
20.
Jun-Ichi Kojima 《The Botanical review》2003,69(1):44-58
Acceptable methods of defining taxon (or clade) names in the draft PhyloCode, or so-called phylogenetic nomenclature, are
“node based,” “stem based,” and “apomorphy based.” All of them define a clade name by pinpointing a node; whereas node-based
and stem-based definitions require two or more taxon “specifiers” to define names, an apomorphy-based definition requires
two specifiers of different types; namely, a single-taxon specifier and a character specifier. The taxon specifier in an apomorphy-based
definition is completely different from the “type” in the Linnaean system. Taxon (or clade) names in the PhyloCode are characterized
in two entirely different manners: One is a name that does not change, either in its orthography or in the contents of the
taxon referred to by it (or its meaning) over time; the other is a name that is just like a pure mark and thus has no meaning.
Communication through such PhyloCode names is very ineffective or impossible. 相似文献