共查询到20条相似文献,搜索用时 31 毫秒
1.
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.
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Peter beim GrabenEmail: |
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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: |
4.
Michael Root 《Biology & philosophy》2009,24(3):375-385
In the United States, the racial and ethnic statistics published by the National Center for Health Statistics (NCHS) assume
that each member of the U.S. population has a race and ethnicity and that if a member is black or white with respect to his
risk of one disease, he is the same race with respect to his risk of another. Such an assumption is mistaken. Race and ethnicity
are taken by the NCHS to be an intrinsic property of members of a population, when they should be taken to depend on interest.
The actual or underlying race or ethnicity of members of a population depends on the risk whose variation within the population
we wish to describe or explain.
相似文献
Michael RootEmail: |
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The recent contribution by Jarmila Kukalová-Peck on Hennigian phylogenetics and hexapod limb evolution is critically evaluated.
相似文献
Michael S. Engel (Corresponding author)Email: |
8.
We develop a formal framework for the optimal allocation of limited resources that includes and clarifies the interplay between
individual optimization and the resulting effects at the population level. As an example, in regard to the evolution of sexual
recombination, the paradox of the twofold cost of sex is avoided by distinguishing between the evolution of recombination
and the subsequent emergence and stability of different mating types as a result of individual optimization within a population
that benefits from recombination.
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John PepperEmail: |
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Peter Palencar Tatyana Prudnikova Frantisek Vacha Michal Kuty 《Journal of molecular modeling》2009,15(8):923-933
Accumulation of reduced pheophytin a (Pheo-D1) in photosystem II reaction center (PSII RC) under illumination at low redox potential is accompanied by changes
in absorbance and circular dichroism spectra. The temperature dependences of these spectral changes have the potential to
distinguish between changes caused by the excitonic interaction and temperature-dependent processes. We observed a conformational
change in the PSII RC protein part and changes in the spatial positions of the PSII RC pigments of the active D1 branch upon
reduction of Pheo-D1 only in the case of high temperature (298 K) dynamics. The resulting absorption difference spectra of
PSII RC models equilibrated at temperatures of 77 K and 298 K were highly consistent with our previous experiments in which
light-induced bleaching of the PSII RC absorbance spectrum was observable only at 298 K. These results support our previous
hypothesis that Pheo-D1 does not interact excitonically with the other chlorins of the PSII RC, since the reduced form of
Pheo-D1 causes absorption spectra bleaching only due to temperature-dependent processes.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
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Michal KutyEmail: |
11.
Robin E. Snyder 《Theoretical Ecology》2009,2(2):79-87
When a pattern of spatial or temporal environmental variation changes, it takes time for populations to reach their new stationary
distributions, and during this time, the competitive landscape is also in flux. As a first step toward understanding community
responses to altered variational regimes, I investigate the convergence of an annual–perennial plant system to its stationary
spatiotemporal distribution following a change in environmental variation. I find that, to good approximation, convergence
is the sum of two separate processes: global convergence, which governs changes in the total population, and local convergence,
which governs population redistribution. While the slower process (global or local) eventually governs convergence, the faster
process may initially dominate if it starts further from its stationary distribution, so that the populations converge quickly
at first, then slow down. That is, when disturbances are spatially heterogeneous, a system may be initially more resilient
under some initial conditions than others.
相似文献
Robin E. SnyderEmail: |
12.
Ostracode shell chemistry is a powerful tool for recording changes of certain dissolved ions in their environment. Such data
are commonly interpreted in terms of change in temperature and salinity, which are then used to offer insights into paleohydrology
and from that paleoclimate. In particular, the changes in Sr/Cashell are believed to reflect changes in salinity, and the changes in Mg/Cashell to reflect both salinity and water temperature. However, the established application of this proxy too often ignores the
complexities involved in the chemical changes accompanying solute evolution, hydrologic change, physical chemistry, and the
autoecology and biology of ostracodes. Chemical changes occur: (1) in the dissolved Mg/Ca and Sr/Ca ratios during solute evolution,
(2) as a consequence of multiple sources of water, but especially ground and surface water interchange as well as evaporation,
(3) as a consequence of different dissolved cation–anion pair formation at various concentrations, and (4) because of bio/ecologic
effects, including seasonality of molting and taxa-specific ionic regulation capabilities. We suggest that changes in shell
chemistry in a stratigraphic sequence tell us when changes occurred in the solutes, but cannot identify what caused those
change(s) in the chemical environment. Inclusion of information from other paleoenvironmental and paleoclimatic proxies that
co-occur with ostracode shells may help to limit the choices amongst possible causes.
相似文献
Emi ItoEmail: |
13.
Threatened species and the spatial concentration of humans 总被引:1,自引:1,他引:0
Public policies that encourage high-density human living arrangements have been predicated explicitly on the assumption that
certain spatial distributions of a fixed-size human population are less environmentally damaging than others. We examine the
empirical validity of this assumption across 127 countries by analyzing whether the concentration of human presence in each
country is related statistically to the percentage of species that were on the IUCN Red List in 2004. Our findings indicate
that concentration of the human population is associated with reduced imperilment among amphibians but increased imperilment
among reptiles, and birds.
相似文献
Ram PanditEmail: |
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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: |
16.
Roger Sansom 《Biology & philosophy》2009,24(4):441-459
One current version of the internalism/externalism debate in evolutionary theory focuses on the relative importance of developmental
constraints in evolutionary explanation. The received view of developmental constraints sees them as an internalist concept
that tend to be shared across related species as opposed to selective pressures that are not. Thus, to the extent that constraints
can explain anything, they can better explain similarity across species, while natural selection is better able to explain
their differences. I challenge both of these aspects of the received view and propose a hierarchical view of constraints.
相似文献
Roger SansomEmail: |
17.
Binding free energy calculations of N-sulphonyl-glutamic acid inhibitors of MurD ligase 总被引:1,自引:0,他引:1
The increasing incidence of bacterial resistance to most available antibiotics has underlined the urgent need for the discovery
of novel efficacious antibacterial agents. The biosynthesis of bacterial peptidoglycan, where the MurD enzyme is involved
in the intracellular phase of UDP-MurNAc-pentapeptide formation, represents a collection of highly selective targets for novel
antibacterial drug design. Structural studies of N-sulfonyl-glutamic acid inhibitors of MurD have made possible the examination of binding modes of this class of compounds,
providing valuable information for the lead optimization phase of the drug discovery cycle. Binding free energies were calculated
for a series of MurD N-sulphonyl-Glu inhibitors using the linear interaction energy (LIE) method. Analysis of interaction energy during the 20-ns
MD trajectories revealed non-polar van der Waals interactions as the main driving force for the binding of these inhibitors,
and excellent agreement with the experimental free energies was obtained. Calculations of binding free energies for selected
moieties of compounds in this structural class substantiated even deeper insight into the source of inhibitory activity. These
results constitute new valuable information to further assist the lead optimization process.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
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Tom SolmajerEmail: |
18.
Studies on the effects of a variety of exogenous and anthropogenic environmental factors, including endocrine disruptors,
heavy metals, UV light, high temperature, and others, on marine organisms have been presented at the 2nd Bilateral Seminar
Italy–Japan held in November 2006. Reports were discussed in order to reveal the current situation of marine ecosystems, aiming
at evaluation and prediction of environmental risks.
相似文献
V. MatrangaEmail: |
19.
Nagayasu Nakanishi Volker Hartenstein David K. Jacobs 《Development genes and evolution》2009,219(6):301-317
We examined the development of the nervous system in the rhopalium, a medusa-specific sensory structure, in Aurelia sp.1 (Cnidaria, Scyphozoa) using confocal microscopy. The rhopalial nervous system appears primarily ectodermal and contains
neurons immunoreactive to antibodies against tyrosinated tubulin, taurine, GLWamide, and FMRFamide. The rhopalial nervous
system develops in an ordered manner: the presumptive gravity-sensing organ, consisting of the lithocyst and the touch plate,
differentiates first; the “marginal center,” which controls swimming activity, second; and finally, the ocelli, the presumptive
photoreceptors. At least seven bilaterally arranged neuronal clusters consisting of sensory and ganglion cells and their neuronal
processes became evident in the rhopalium during metamorphosis to the medusa stage. Our analysis provides an anatomical framework
for future gene expression and experimental studies of development and functions of scyphozoan rhopalia.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
相似文献
David K. Jacobs (Corresponding author)Email: |
20.
Terry Harmer 《Cluster computing》2007,10(3):277-285
Gridcast is an R&D project investigating grid ideas and technologies in the broadcasting technical infrastructure. In this
paper I discuss the business and technical issues in building infrastructures to support broadcasters and outline the structure
of the Gridcast grid-based service oriented architecture for broadcasting playout support.
相似文献
Terry HarmerEmail: |