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1.
One of the distinct characteristics of computing platforms shared by multiple users such as a cluster and a computational
grid is heterogeneity on each computer and/or among computers. Temporal heterogeneity refers to variation, along the time
dimension, of computing power available for a task on a computer, and spatial heterogeneity represents the variation among
computers. In minimizing the average parallel execution time of a target task on a spatially heterogeneous computing system, it is not optimal to distribute the target task linearly proportional
to the average computing powers available on computers. In this paper, effects of the temporal and spatial heterogeneity on
performance of a target task have been analyzed in terms of the mean and standard deviation of parallel execution time. Based
on the analysis results, an approach to load balancing for minimizing the average parallel execution time of a target task
is described. The proposed approach whose validity has been verified through simulation considers temporal and spatial heterogeneities
in addition to the average computing power on each computer.
相似文献
Soo-Young Lee (Corresponding author)Email: |
2.
Roger Sansom 《Biology & philosophy》2008,23(4):475-491
I show that gene regulation networks are qualitatively consistent and therefore sufficiently similar to linearly seperable
connectionist networks to warrant that the connectionist framework be applied to gene regulation. On this view, natural selection
designs gene regulation networks to overcome the difficulty of development. I offer some general lessons about their evolvability
that can be learned by examining the generic features of connectionist networks.
相似文献
Roger SansomEmail: |
3.
Srdjan Ostojic Nicolas Brunel Vincent Hakim 《Journal of computational neuroscience》2009,26(3):369-392
We investigate how synchrony can be generated or induced in networks of electrically coupled integrate-and-fire neurons subject
to noisy and heterogeneous inputs. Using analytical tools, we find that in a network under constant external inputs, synchrony
can appear via a Hopf bifurcation from the asynchronous state to an oscillatory state. In a homogeneous net work, in the oscillatory
state all neurons fire in synchrony, while in a heterogeneous network synchrony is looser, many neurons skipping cycles of
the oscillation. If the transmission of action potentials via the electrical synapses is effectively excitatory, the Hopf
bifurcation is supercritical, while effectively inhibitory transmission due to pronounced hyperpolarization leads to a subcritical
bifurcation. In the latter case, the network exhibits bistability between an asynchronous state and an oscillatory state where
all the neurons fire in synchrony. Finally we show that for time-varying external inputs, electrical coupling enhances the
synchronization in an asynchronous network via a resonance at the firing-rate frequency.
相似文献
Srdjan OstojicEmail: |
4.
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: |
5.
Sub-Antarctic Marion Island has had a permanent research station for 50 years and the islands Wandering Albatrosses have been intensively studied for 20 years. The reactions of breeding birds to approaches by a human on foot were recorded. Three response variables were calculated: intensity of vocal reaction (IVR), intensity of non-vocal reaction (INR) and overall response index (ORI). At 5 m from the nest, twice as many birds stood and/or vocalised as at 15 m. Nearest neighbour distance, age and gender did not explain individual variability of responses. Study colony birds had higher IVR scores than non-study colony birds; birds at colonies closest to the station had the highest ORI scores. A better breeding record was associated with lower IVR and ORI scores, but a causative relationship remains to be demonstrated. A minimum viewing distance of 25 m is recommended for breeding Wandering Albatrosses.
相似文献
Marienne S. de VilliersEmail: Fax: +27-21-6503434 |
John CooperEmail: |
Peter G. RyanEmail: |
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.
It is basic question in biology and other fields to identify the characteristic properties that on one hand are shared by
structures from a particular realm, like gene regulation, protein–protein interaction or neural networks or foodwebs, and
that on the other hand distinguish them from other structures.
We introduce and apply a general method, based on the spectrum of the normalized
graph Laplacian, that yields representations, the spectral plots, that allow us
to find and visualize such properties systematically. We present such
visualizations for a wide range of biological networks and compare them with
those for networks derived from theoretical schemes. The differences that we find
are quite striking and suggest that the search for universal properties of
biological networks should be complemented by an understanding of more specific
features of biological organization principles at different scales.
相似文献
Jürgen JostEmail: |
8.
A key point in the analysis of dynamical models of biological systems is to handle systems of relatively high dimensions.
In the present paper we propose a method to hierarchically organize a certain type of piecewise affine (PWA) differential
systems. This specific class of systems has been extensively studied for the past few years, as it provides a good framework
to model gene regulatory networks. The method, shown on several examples, allows a qualitative analysis of the asymptotic
behavior of a PWA system, decomposing it into several smaller subsystems. This technique, based on the well-known strongly
connected components decomposition, is not new. However, its adaptation to the non-smooth PWA differential equations turns
out to be quite relevant because of the strong discrete structure underlying these equations. Its biological relevance is
shown on a 7-dimensional PWA system modeling the gene network responsible for the carbon starvation response in Escherichia coli.
相似文献
Laurent Tournier (Corresponding author)Email: |
Jean-Luc GouzéEmail: |
9.
10.
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: |
11.
The French airborne pollen monitoring network (RNSA) is currently regrouping 70 Hirst-type pollen traps covering the whole
French territory. The aim of this paper is to introduce a simple statistical methodology that can be used to characterize
pollen spatial variation. This pilot study is restricted to a limited portion of the RNSA network (18 monitoring stations),
eight taxa of allergenic relevance, and a 3-year period (2003–2005). The first step of the approach consisted in quantifying
the trap-to-trap pollen similarities on the basis of an original index, called mean Pollinic Distance (mPD), that relies on
the comparison of pollen concentration time series. Regression analyses were next conducted with different spatial variables.
Distance, latitude and altitude differences were identified as significant predictors of pollen variations, as measured by
mPD. In order to further characterize pollen spatial properties, cluster analysis was performed with mPD as the distance estimate.
Interestingly, the clusters of sites identified on the basis of the similarity of their pollen profiles, correspond to distinct
geographic areas that might be interpreted as homogeneous air masses. The results have major implications for monitoring networks
management since they provide an objective basis (1) for choosing the relevant scale to elaborate and supply pollen-related
information, and (2) for optimizing networks configuration.
相似文献
Camille RieuxEmail: |
12.
13.
Michael Weisberg 《Biology & philosophy》2006,21(5):623-645
This paper is an interpretation and defense of Richard Levins’ “The Strategy of Model Building in Population Biology,” which
has been extremely influential among biologists since its publication 40 years ago. In this article, Levins confronted some
of the deepest philosophical issues surrounding modeling and theory construction. By way of interpretation, I discuss each
of Levins’ major philosophical themes: the problem of complexity, the brute-force approach, the existence and consequence
of tradeoffs, and robustness analysis. I argue that Levins’ article is concerned, at its core, with justifying the use of
multiple, idealized models in population biology.
相似文献
Michael WeisbergEmail: |
14.
15.
Jane E. Schultz 《Journal of bioethical inquiry》2007,4(2):93-102
In researching the biomedically-engineered drug Neulasta (filgrastim), a breast cancer patient becomes aware of the extent
to which knowledge about the development and marketing of drugs influences her decisions with regard to treatment. Time spent
on understanding the commercial interests of insurers and pharmaceutical companies initially thwarts but ultimately aids the
healing process. This first-person narrative calls for physicians to recognize that the alignment of commercial interests
transgresses the patient’s humanity.
相似文献
Jane E. SchultzEmail: |
16.
Chris Haufe 《Biology & philosophy》2008,23(1):115-128
The importance of mate choice and sexual selection has been emphasized by the majority of evolutionary psychologists. This
paper assesses three cases of work on mate choice and sexual selection in evolutionary psychology: David Buss on cross-cultural
human mate preferences, Randy Thornhill and Steve Gangestad on the link between mate preferences and fluctuating asymmetry,
and Geoffrey Miller on the role of Fisher’s runaway process in human evolution. A mixture of conceptual and empirical problems
in each case highlights the general weakness of work in evolutionary psychology on these issues.
相似文献
Chris HaufeEmail: |
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.
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: |
19.
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: |
20.