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1.
This paper introduces a threshold policy with hysteresis (TPH) for the control of one-predator one-prey models. The models studied are the Lotka–Volterra and Rosenzweig–MacArthur
two species density-dependent predator–prey models and the Arditi–Ginzburg nondimensional ratio-dependent model. The proposed
policy (TPH) changes the dynamics of the system in such a way that a bounded oscillation is achieved confined to a region
that does not allow extinction of either species. The policy can be designed by a suitable choice of so called virtual equilibrium
points in a simple and intuitive manner.
相似文献
Amit Bhaya (Corresponding author)Email: |
2.
Ewa Puchalska Barbara Czajkowska Magorzata Kiekiewicz 《Acta Physiologiae Plantarum》2008,30(2):225-232
Our investigations suggest that the usually observed avoidance by O. ununguis of current year’s twigs of P. glauca ‘Conica’ as a place for feeding and development may be connected with their morphological and anatomical structure as well
their biochemical composition. Needles of the current year’s twigs were covered with a thicker layer of wax and formed more
extensive epidermis cell walls, in comparison with needles of 1-year-old twigs. Young needles also showed lower concentration
of reducing sugars and soluble proteins, which might additionally reduce their nutritional suitability for mite development.
Differences were also found between the 1-year-old growth and current growth in contribution of essential oils and a range
of other compounds. Further analyses of the effect of these compounds on mite behavior may provide additional explanation
of the feeding preferences of the mite.
相似文献
Barbara CzajkowskaEmail: |
3.
The performance of synchronous parallel polynomial root extraction on a ring multicomputer 总被引:1,自引:0,他引:1
Hamid Sarbazi-Azad 《Cluster computing》2007,10(2):167-174
In this paper, a parallel algorithm for computing the roots of a given polynomial of degree n on a ring of processors is proposed.
The algorithm implements Durand–Kerner’s method and consists of two phases: initialisation, and iteration. In the initialisation
phase all the necessary preparation steps are realised to start the parallel computation. It includes register initialisation
and initial approximation of roots requiring 3n−2 communications, 2 exponentiation, one multiplications, 6 divisions, and 4n−3 additions. In the iteration phase, these initial approximated roots are corrected repeatedly and converge to their accurate
values. The iteration phase is composed of some iteration steps, each consisting of 3n communications, 4n+3 additions, 3n+1 multiplications, and one division.
相似文献
Hamid Sarbazi-AzadEmail: Email: |
4.
Lévy Flights in Dobe Ju/’hoansi Foraging Patterns 总被引:1,自引:0,他引:1
Clifford T. Brown Larry S. Liebovitch Rachel Glendon 《Human ecology: an interdisciplinary journal》2007,35(1):129-138
We analyzed data on Ju/’hoansi hunter–gatherer foraging patterns and found that their movements between residence camps can
be modeled as a Lévy flight. The step lengths of their movements scale as a power law with an exponent μ = 1.97. Their wait times (residence times) at the camps also scale as a power law (μ = 1.45). A Lévy flight with step lengths μ = 2 is an optimal search pattern for scarce, randomly located targets; thus, the Ju/’hoansi foraging pattern may approach
an optimal search in this area of sparse plant and animal resources. These findings affect the application of optimal foraging
theory to humans in anthropology and archaeology because they alter the way in which search and travel times should be quantified.
These results may also carry implications for the study of other patterns of human movement, such as demic diffusion and migration.
相似文献
Clifford T. BrownEmail: |
5.
Peter Godfrey-Smith 《Biology & philosophy》2007,22(3):429-437
Jablonka and Lamb's claim that evolutionary biology is undergoing a ‘revolution’ is queried. But the very concept of revolutionary
change has uncertain application to a field organized in the manner of contemporary biology. The explanatory primacy of sequence
properties is also discussed.
相似文献
Peter Godfrey-SmithEmail: |
6.
Debates over adaptationism can be clarified and partially resolved by careful consideration of the ‘grain’ at which evolutionary
processes are described. The framework of ‘adaptive landscapes’ can be used to illustrate and facilitate this investigation.
We argue that natural selection may have special status at an intermediate grain of analysis of evolutionary processes. The
cases of sickle-cell disease and genomic imprinting are used as case studies.
相似文献
Peter Godfrey-SmithEmail: |
7.
Event-related brain potentials (ERP) are important neural correlates of cognitive processes. In the domain of language processing,
the N400 and P600 reflect lexical-semantic integration and syntactic processing problems, respectively. We suggest an interpretation
of these markers in terms of dynamical system theory and present two nonlinear dynamical models for syntactic computations
where different processing strategies correspond to functionally different regions in the system’s phase space.
相似文献
Peter beim GrabenEmail: |
8.
Renuka M. Sharma 《Journal of bioethical inquiry》2007,4(3):181-192
This paper discusses the persistent devaluation of the girl child in India and the link between the entrenched perception
of female valuelessness and the actual practice of infanticide of girl babies or foetuses. It seeks to place female infanticide,
or ‘gendercide,’ within the context of Western-derived conceptions of ethics, justice and rights. To date, current ethical
theories and internationally purveyed moral frameworks, as well as legal and political declarations, have fallen short of
an adequate moral appraisal of infanticide. This paper seeks to rethink the issue.
相似文献
Renuka M. SharmaEmail: |
9.
J. Stephen Athens 《Biological invasions》2009,11(7):1489-1501
Paleoenvironmental and archaeological investigations from the ’Ewa Plain of O’ahu provide insight into the problem of understanding
lowland native forest loss in Hawai’i. Data from pollen analysis of a pond core record, avian paleontology, and archeology,
document a precipitous decline of the native forest starting before Polynesian settlement on the ’Ewa Plain but after Polynesian
colonization of O’ahu. It is hypothesized that rats, introduced by Polynesian colonizers, increased exponentially in the absence
of significant predators or competitors, feeding on a largely endemic vegetation that had evolved in the absence of mammalian
predators. Rats radiated ahead of human colonizers on O’ahu, eating their way through the vegetation, perhaps before the colonizers
had encountered much of the pristine lowland forest into which the rats had radiated. This hypothesis is supported by several
observations, including the almost complete absence of extinct or extirpated avian faunal remains in archaeological deposits,
the present distribution of endemic vegetation in Hawai’i, rat ecology, population biology, and other evidence.
相似文献
J. Stephen AthensEmail: |
10.
Philip Richard Sullivan 《Biology & philosophy》2009,24(1):65-79
This paper demonstrates that the human visual system, the primary sensory conduit for primates, processes ambient energy in
a way that obligatorily constructs the objects that we ineluctably perceive. And since our perceptual apparatus processes
information only in terms of objects (along with the properties and movements of objects), we are limited in our ability to comprehend ‘what
is’ when we move beyond our ordinary world of midsize objects—as, for example, when we address the micro microworld of quantum
physics.
相似文献
Philip Richard SullivanEmail: |
11.
Sciences able to identify appropriate analytical units for their domain, their natural kinds, have tended to be more progressive.
In the biological sciences, evolutionary natural kinds are adaptations that can be identified by their common history of selection
for some function. Human brains are the product of an evolutionary history of selection for component systems which produced
behaviours that gave adaptive advantage to their hosts. These structures, behaviour production systems, are the natural kinds
that psychology seeks. We argue these can be identified deductively by classing behaviour first according to its level of
behavioural control. Early animals in our lineage used only reactive production, Vertebrates evolved motivation, and later Primates developed executive control. Behaviour can also be classified by the type of evolutionary benefit it bestows: it can deliver either immediate
benefits (food, gametes), improvements in the individual’s position with respect to the world (resource access, social status),
or improvements in the ability to secure future benefits (knowledge, skill). Combining history and function implies the existence
of seven types of behaviour production systems in human brains responsible for reflexive, instinctual, exploratory, driven, emotional, playful and planned behaviour. Discovering scientifically valid categories of behaviour can provide a fundamental taxonomy and common language
for understanding, predicting and changing behaviour, and a way of discovering the organs in the brain––its natural kinds––that
are responsible for behaviour.
相似文献
Valerie CurtisEmail: |
12.
Peter beim Graben Dimitris Pinotsis Douglas Saddy Roland Potthast 《Cognitive neurodynamics》2008,2(2):79-88
We construct a mapping from complex recursive linguistic data structures to spherical wave functions using Smolensky’s filler/role
bindings and tensor product representations. Syntactic language processing is then described by the transient evolution of
these spherical patterns whose amplitudes are governed by nonlinear order parameter equations. Implications of the model in
terms of brain wave dynamics are indicated.
Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users.
相似文献
Peter beim GrabenEmail: |
13.
Luis Emilio Bruni 《Biosemiotics》2008,1(1):113-130
This article considers categorical perception (CP) as a crucial process involved in all sort of communication throughout the
biological hierarchy, i.e. in all of biosemiosis. Until now, there has been consideration of CP exclusively within the functional
cycle of perception–cognition–action and it has not been considered the possibility to extend this kind of phenomena to the
mere physiological level. To generalise the notion of CP in this sense, I have proposed to distinguish between categorical
perception (CP) and categorical sensing (CS) in order to extend the CP framework to all communication processes in living
systems, including intracellular, intercellular, metabolic, physiological, cognitive and ecological levels. The main idea
is to provide an account that considers the heterarchical embeddedness of many instances of CP and CS. This will take me to relate the hierarchical nature of categorical sensing and perception
with the equally hierarchical issues of the “binding problem”, “triadic causality”, the “emergent interpretant” and the increasing
semiotic freedom observed in biological and cognitive systems.
相似文献
Luis Emilio BruniEmail: |
14.
The Gitksan and Wet’suwet’en of Northwestern British Columbia formerly used landscape burning to manage patches of black huckleberry
(Vaccinium membranaceum), the most important plant resource of their seasonal round. In view of its significance one might postulate that managed
sites would conform to a biophysical or ecological type to maximize return for effort. However, a survey of a number of traditionally
managed sites indicated that managed sites are characterized by wide variation in biophysical attributes including elevation,
aspect and moisture regime, while proximity to fishing sites, village sites, or sites for harvest of alpine resources proved
to be a common factor in known historic berry patch sites. We conclude that characterization of the ideal site type for aboriginal
V. membranaceum management must include the economy and social institutions of the local First Nations and requires an enhanced appreciation
for the sophistication of the strategies and techniques employed in their management and utilization of the species.
相似文献
Leslie Main Johnson (Corresponding author)Email: |
15.
John L. Markley David J. Aceti Craig A. Bingman Brian G. Fox Ronnie O. Frederick Shin-ichi Makino Karl W. Nichols George N. Phillips Jr. John G. Primm Sarata C. Sahu Frank C. Vojtik Brian F. Volkman Russell L. Wrobel Zsolt Zolnai 《Journal of structural and functional genomics》2009,10(2):165-179
The Center for Eukaryotic Structural Genomics (CESG) is a “specialized” or “technology development” center supported by the
Protein Structure Initiative (PSI). CESG’s mission is to develop improved methods for the high-throughput solution of structures
from eukaryotic proteins, with a very strong weighting toward human proteins of biomedical relevance. During the first three
years of PSI-2, CESG selected targets representing 601 proteins from Homo sapiens, 33 from mouse, 10 from rat, 139 from Galdieria sulphuraria, 35 from Arabidopsis thaliana, 96 from Cyanidioschyzon merolae, 80 from Plasmodium falciparum, 24 from yeast, and about 25 from other eukaryotes. Notably, 30% of all structures of human proteins solved by the PSI Centers
were determined at CESG. Whereas eukaryotic proteins generally are considered to be much more challenging targets than prokaryotic
proteins, the technology now in place at CESG yields success rates that are comparable to those of the large production centers
that work primarily on prokaryotic proteins. We describe here the technological innovations that underlie CESG’s platforms
for bioinformatics and laboratory information management, target selection, protein production, and structure determination
by X-ray crystallography or NMR spectroscopy.
相似文献
John L. MarkleyEmail: |
16.
Richard O. Clemmer 《Dialectical Anthropology》2009,33(1):51-70
In 1921 the U.S. Office of Indian Affairs (OIA) attempted to suppress ritual public performances in the Southwestern Pueblos.
Several reams of documenting text were used to support this authorizing text. These documenting texts were affidavits purporting to describe “degrading tendencies” and “immoral relations” in the Puebloan
habitus. The OIA used these sensationalized representations of the habitus of Native Americans’ communities to promote and justify the policy of forced acculturation in the waning days of its implementation.
What is perplexing is that these supporting texts were trotted out so late, decades after the major thrusts of the forced
acculturation program had first been put into play. My purpose is to analyze the place of these texts in the forced acculturation
program. I suggest, following Anne McClintock (1995) that the obsessive fascination that the public performances seem to have held for those who reported on and condemned them,
represent a layered and complex intertwining of ambivalence about domestic social relations and gender with confusion about
culture and labor. Examining a slice of the U.S. Government’s policy of forced acculturation in a corner of the Native American
world reveals a potentially implosive anxiety of reconciling the imposition of a desired mode of production with the persistence
of a habitus perceived as celebrating the violation of appropriate domesticity.
相似文献
Richard O. ClemmerEmail: |
17.
Stefan Artmann 《Biosemiotics》2009,2(1):31-38
Though the formal coherence and empirical utility of Marcello Barbieri’s concept of organic code have been starting to become
established, a general conception of how the semantics of organic codes is related to the pragmatics of their use is still
missing. Barbieri took a first step towards such a conception by distinguishing three types of semiosis in living systems:
manufacturing, signalling, and interpretive semiosis. This paper integrates Barbieri’s distinction into Roman Jakobson’s systematization
of possible functions of messages in order to propose a general conception of possible types of semiosis in living systems.
As a result, Barbieri’s thesis that manufacturing and signalling semiosis are basic types of semiosis, can be confirmed and
completed communication-theoretically.
相似文献
Stefan ArtmannEmail: |
18.
Patrick Forber 《Biology & philosophy》2009,24(2):247-266
Evolutionary biology, indeed any science that attempts to reconstruct prehistory, faces practical limitations on available
data. These limitations create the problem of contrast failure: specific observations may fail to discriminate between rival evolutionary hypotheses. Assessing the risk of contrast failure
provides a way to evaluate testing protocols in evolutionary science. Here I will argue that part of the methodological critique
in the Spandrels paper involves diagnosing contrast failure problems. I then distinguish the problem of contrast failure from the more familiar
philosophical problem of underdetermination, and demonstrate how contrast failure arises in scientific practice with an investigation
into Lewontin and White’s (Evolution 14:116–129, 1960) estimation of an adaptive landscape.
相似文献
Patrick ForberEmail: |
19.
Kevin K. Lin Eric Shea-Brown Lai-Sang Young 《Journal of computational neuroscience》2009,27(1):135-160
We study the reliability of layered networks of coupled “type I” neural oscillators in response to fluctuating input signals. Reliability means that
a signal elicits essentially identical responses upon repeated presentations, regardless of the network’s initial condition.
We study reliability on two distinct scales: neuronal reliability, which concerns the repeatability of spike times of individual neurons embedded within a network, and pooled-response reliability, which concerns the repeatability of total synaptic outputs from a subpopulation of the neurons in a network. We find that
neuronal reliability depends strongly both on the overall architecture of a network, such as whether it is arranged into one
or two layers, and on the strengths of the synaptic connections. Specifically, for the type of single-neuron dynamics and
coupling considered, single-layer networks are found to be very reliable, while two-layer networks lose their reliability
with the introduction of even a small amount of feedback. As expected, pooled responses for large enough populations become
more reliable, even when individual neurons are not. We also study the effects of noise on reliability, and find that noise
that affects all neurons similarly has much greater impact on reliability than noise that affects each neuron differently.
Qualitative explanations are proposed for the phenomena observed.
相似文献
Eric Shea-BrownEmail: |
20.
Does Investment in the Sexes Differ When Fathers Are Absent? 总被引:1,自引:1,他引:0
Mhairi A. Gibson 《Human nature (Hawthorne, N.Y.)》2008,19(3):263-276
This study examines child survival and growth in a patrilineal Ethiopian community as a function of father absence and sex.
In line with evolutionary predictions for sex-biased parental investment, the absence of a father and associated constraints
on household resources is more detrimental for sons’ than daughters’ survival in infancy. Father absence doubles a son’s risk
of dying in infancy but has a positive influence on the well-being of female members of the household, improving daughter
survival, growth, and maternal nutritional status. Lack of paternal investment may be compensated for by other matrilateral
kin through increased reciprocity between mother, daughter, and sister.
相似文献
Mhairi A. GibsonEmail: |