共查询到20条相似文献,搜索用时 31 毫秒
1.
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: |
2.
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: |
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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.
Fabien Marpeau Aditya Barua Krešimir Josić 《Journal of computational neuroscience》2009,26(3):445-457
The stochastic integrate and fire neuron is one of the most commonly used stochastic models in neuroscience. Although some
cases are analytically tractable, a full analysis typically calls for numerical simulations. We present a fast and accurate
finite volume method to approximate the solution of the associated Fokker-Planck equation. The discretization of the boundary
conditions offers a particular challenge, as standard operator splitting approaches cannot be applied without modification.
We demonstrate the method using stationary and time dependent inputs, and compare them with Monte Carlo simulations. Such
simulations are relatively easy to implement, but can suffer from convergence difficulties and long run times. In comparison,
our method offers improved accuracy, and decreases computation times by several orders of magnitude. The method can easily
be extended to two and three dimensional Fokker-Planck equations.
相似文献
Fabien MarpeauEmail: |
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7.
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: |
8.
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: |
9.
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: |
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Pete Beckman Kamil Iskra Kazutomo Yoshii Susan Coghlan Aroon Nataraj 《Cluster computing》2008,11(1):3-16
We investigate operating system noise, which we identify as one of the main reasons for a lack of synchronicity in parallel
applications. Using a microbenchmark, we measure the noise on several contemporary platforms and find that, even with a general-purpose
operating system, noise can be limited if certain precautions are taken. We then inject artificially generated noise into
a massively parallel system and measure its influence on the performance of collective operations. Our experiments indicate
that on extreme-scale platforms, the performance is correlated with the largest interruption to the application, even if the
probability of such an interruption on a single process is extremely small. We demonstrate that synchronizing the noise can
significantly reduce its negative influence.
相似文献
Aroon NatarajEmail: |
13.
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: |
14.
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: |
15.
Vladimir G. Ivancevic 《Cognitive neurodynamics》2009,3(3):281-293
The prediction and prevention of traumatic brain injury is a very important aspect of preventive medical science. This paper
proposes a new coupled loading-rate hypothesis for the traumatic brain injury (TBI), which states that the main cause of the TBI is an external Euclidean jolt, or SE(3)-jolt, an impulsive loading that strikes the head in several coupled degrees-of-freedom simultaneously. To show this, based
on the previously defined covariant force law, we formulate the coupled Newton–Euler dynamics of brain’s micro-motions within the cerebrospinal fluid and derive from it
the coupled SE(3)-jolt dynamics. The SE(3)-jolt is a cause of the TBI in two forms of brain’s rapid discontinuous deformations: translational dislocations and rotational
disclinations. Brain’s dislocations and disclinations, caused by the SE(3)-jolt, are described using the Cosserat multipolar viscoelastic continuum brain model.
相似文献
Vladimir G. IvancevicEmail: |
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Abhijeet Bardapurkar 《Evolution》2008,1(3):299-305
This paper critically reviews and characterizes the student's causal-explanatory understanding; this is done as a step toward
explicating the problematic of evolution education as it concerns the cognitive difficulties in understanding Darwin's theory of natural selection. The review concludes that the student's understanding is fundamentally different from Darwin's, for
the student understands evolutionary change as necessary individual transformation caused by the transformative action of
various physical and behavioral factors. This is in complete contrast to Darwin's (and even the Darwinian's, for that matter)
understanding of evolutionary change as a change caused by accumulative selection. Hence, to understand natural selection,
the student has to learn to “see” how the accumulative selection causes evolutionary change.
相似文献
Abhijeet BardapurkarEmail: |
18.
Brett Calcott 《Biology & philosophy》2008,23(5):639-657
According to Pigliucci and Kaplan, there is a revolution underway in how we understand fitness landscapes. Recent models suggest
that a perennial problem in these landscapes—how to get from one peak across a fitness valley to another peak—is, in fact,
non-existent. In this paper I assess the structure and the extent of Pigliucci and Kaplan’s proposed revolution and argue
for two points. First, I provide an alternative interpretation of what underwrites this revolution, motivated by some recent
work on model-based science. Second, I show that the implications of this revolution need to carefully assessed depending on question being asked,
for peak-shifting is not central to all evolutionary questions that fitness landscapes have been used to explore.
相似文献
Brett CalcottEmail: |
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20.
An ab initio computational density functional theory (DFT) was used to study the formation of the first cyclic molecule (phenyl)
initiated by the ethynyl radical (C2H•). The study covers a competition reaction between the addition reactions of C2H• with ethyne (C2H2) and some molecular re-arrangement schemes. The minimum energy paths of the preferred cyclic formation route were characterized.
A thorough thermochemical analysis was performed by evaluating the differences in the energy of activation (ΔE), enthalpy
(ΔH), and Gibb's free energy (ΔG) of the optimized stable and transition state (TS) molecules. The reaction temperatures were
set to normal (T = 298 K) and combustion (T = 1,200 K) conditions.
相似文献
Romero M. SantiagoEmail: |