BibSonomy publications for /concept/tag/CONNECTIVITYThu Jul 03 10:37:30 CEST 2008PLoS Biologye1597Mapping the Structural Core of Human Cerebral Cortex62008cortex braintopology connectivity Structurally segregated and functionally specialized regions of the human cerebral cortex are interconnected by a dense network of cortico-cortical axonal pathways. By using diffusion spectrum imaging, we noninvasively mapped these pathways within and across cortical hemispheres in individual human participants. An analysis of the resulting large-scale structural brain networks reveals a structural core within posterior medial and parietal cerebral cortex, as well as several distinct temporal and frontal modules. Brain regions within the structural core share high degree, strength, and betweenness centrality, and they constitute connector hubs that link all major structural modules. The structural core contains brain regions that form the posterior components of the human default network. Looking both within and outside of core regions, we observed a substantial correspondence between structural connectivity and resting-state functional connectivity measured in the same participants. The spatial and topological centrality of the core within cortex suggests an important role in functional integration.Thu Jun 19 13:57:22 CEST 2008EcologyJuly71844--1855ON METAPOPULATION RESISTANCE TO DRIFT AND EXTINCTION872006biodiversity metapopulation SPOM fragmentation stochastic_patch_occupancy_model landscape connectivity eigenvalue_effective_size matrix_analysis Cricetus_cricetus The spatial configuration of metapopulations (numbers, sizes, and
localization of patches) affects their ability to resist demographic
extinction and genetic drift, but sometimes with opposite effects.
Small and isolated patches, for instance, contribute marginally to
demography but may play a large role in genetics by maintaining a
sizeable amount of genetic variance among demes. In source–sink
systems, similarly, connectivity may be beneficial in terms of effective
size, but detrimental in terms of survival, by lowering the reproductive
value of source populations. How to reconcile these opposite effects?
Here we propose an analytical framework that integrates fixation
time (ability to resist genetic drift) and extinction time (ability
to resist demographic extinction) into a single index of resistance,
measuring the ability of a metapopulation to maintain its demo-genetic
integrity. We then illustrate with numerical examples how conflicting
demands may be resolved.Tue Apr 22 10:36:30 CEST 2008Physica A: Statistical Mechanics and its ApplicationsJun1-4207--220Spin models on random lattices2812000disorder Connectivity 15Wed Apr 16 12:59:10 CEST 2008Games and Culture113-25{Convergence, Connectivity, and the Case of Japanese Mobile Gaming}32008convergence mobile_games lv_crossmedia_2 mobile_telephony cross-media connectivity Japan The specificities of Japanese mobile telephony are giving rise to new cultural economies of games production and engendering new paradigms of gameplay. These topical developments have considerable technosocial bearing and consequence. The tension between the virtual and the actual resides at the heart of topical debates about the modalities of co-presence in mobile telephony. The potential loss of anonymity in location-based mobile gaming and the increasing awareness that mobile games are mostly played at home add considerable complexity to the already-blurred boundaries of physical and virtual co-presence. The micronarratives of such newly configured and articulated social tropes arguably need to be incorporated into macroperspectives on convergence culture if only to invest the latter with additional levels of nuance and complexity. Japanese mobile gaming therefore has strategic utility in this article as a situated context for analyzing the localized cultural politics of convergence and connectivity in mobile telephony.
Sun Apr 13 15:33:20 CEST 2008Hershey, PAKnowledge Networks: Innovation through Communities of Practice12133--141Viable Communities within Organizational Contexts: Creating and Sustaining Viability in Communities of Practice at Siemens AG2004Technology_and_Social_Issues IT_Platform Organizational_Context KM Face-to-Face Set_of_Guidelines Viability Community_Building Facilitation Connectivity Common_Focus CoP Meetings Values Knowledge_Management Community_of_Practice This chapter is about the question of what creates and sustains viability in Communities of Practice (CoPs) embedded in an organizational context. Experience with successful CoPs at Siemens AG has shown that even though most of them differ greatly from each other in many aspects, they all share five common factors that are necessary for the viability of a CoP. These five factors are introduced in the following pages. They represent an approach that can be used to analyse and improve CoPs that do not seem to be viable and as a guide for CoP members and moderators to maintain viability in their own CoPs.Wed Mar 19 12:51:27 CET 2008New York, NY, USAWSDM '08: Proceedings of the international conference on Web search and web data mining129--138Connectivity structure of bipartite graphs via the KNC-plot2008intersection structure bit connectivity vector bipartite graph Mon Oct 22 16:18:59 CEST 2007New York, NY, USASIGMOD Rec.458--64Ontologies and semantics for seamless connectivity332004seamless connectivity semantic Sat Aug 18 13:22:24 CEST 2007MayConnectivity and the Origin of Inertia2003connectivity curvature mass minkowski origin inertia Newton's Second Law defines inertial mass as the ratio of the applied force
on an object to the responding acceleration of the object (viz., F=ma). Objects
that exhibit finite accelerations under finite forces are described as being
"massive'' and this mass has usually been considered to be an innate property
of the particles composing the object. However mass itself is never directly
measured. It is inertia, the reaction of the object to impressed forces, that
is measured. We show that the effects of inertia are equally well explained as
a consequence of the vacuum fields acting on massless particles travelling in
geodesic motion. In this approach, the vacuum fields in the particle's history
define the curvature of the particle's spacetime. The metric describing this
curvature implies a transformation to Minkowski spacetime, which we call the
Connective transformation. Application of the Connective transformation
produces the usual effects of inertia when observed in Minkowski spacetime,
including hyperbolic motion in a static electric field (above the vacuum) and
uniform motion following an impulse. In the case of the electromagnetic vacuum
fields, the motion of the massless charge is a helical motion that can be
equated to the particle spin of quantum theory. This spin has the properties
expected from quantum theory, being undetermined until "measured'' by applying
a field, and then being found in either a spin up or spin down state.
Furthermore, the zitterbewegung of the charge is at the speed of light, again
in agreement with quantum theory. Connectivity also allows for pair creation as
the Connective transformation can transform positive time intervals in the
particle spacetime to negative time intervals in Minkowski spacetime.Wed Jun 20 10:16:09 CEST 2007Genova, ItalyAbstract Book of the XXIII IUPAP International Conference on Statistical Physics9-13 JulyEffect of defects distributions on phase transitions in crystals2007statphys23 indexes transition topic-2 connectivity critical phase distribution We consider close-packed structure with defects, which undergoes structural phase transition, and we investigate dependence of critical exponents on distribution of defects.
We do not consider single-domain crystals with randomly distributed defects. We discuss the growth condition which of lead to inhomogeneous distribution of defects over a sample [1].
We consider close-packed structure with defects as result of growth process. As a result we obtain some structure which represents a network. Symmetry of such structure is a symmetry corresponding graph. Irreducible representation (non identity) groups of graph define transformation properties of the order parameter. Integer basis of considered irreducible representation allows to write down free energy and to define corresponding critical indexes. We in details analyze a case when presence of defects induces structure with incommensurate or quasicrystal ordering [2]. The structure such space graph can be obtained as a projection highly dimensional regular graph [3]. The point group symmetry of such structure is isomorphic to permutation group. Hence, for phase transitions without change of an elementary cell volume, a transformation property of the order parameter is defined non identity irreducible representation of the permutation group.
Using concrete algorithms for the growth process, it is possible to introduce corresponding equation the solution of which is distribution functions of defects in structure [4]. For the analysis of defects distribution dependence critical exponents, we introduce a free energy functional, which depends on an order parameter and on connectivity distribution of defects of structure. The symmetry of an order parameter is defined by an irreducible representation of a space group of structure. After the procedure an average of a free energy functional on connectivity of defects (practically it implies calculation a moments of the distribution) we obtain, that the critical behavior strongly depends on the form of the distribution function. We consider a case when the solution the equation for growth process leads to fractal distribution of defects connectivity, namely, to Tsallis distribution [5]. We show that the critical behavior strongly depended on the form distribution of connections and differs strongly from mean - field behavior.
References\\
1) A.P. Levanyuk, A.S. Sigov, Defects and structural phase transition (Taylor and Francis, 1988).\\
2) T. Janssen, A. Janner, Advanced in physics, 36, n.5, 519 (1987).\\
3) F. Harary, Graph theory (Addison-Wesley, Reading, MA, 1969).\\
4) R. Albert, A.-L. Barabasi, Rev. Mod. Phys. 74, 47 (2002).\\
5) C. Tsallis, Braz. J. Phys., 29:1 (1999).Wed Jun 20 10:16:09 CEST 2007Genova, ItalyAbstract Book of the XXIII IUPAP International Conference on Statistical Physics9-13 JulyStatics and dynamics of a sparsely connected oscillator network2007oscillator topic-11 theory statphys23 connectivity finite replica network dynamical \hspace{0.3cm}We study interacting systems where the network of interactions
between the different units is of a sparse, random and often complex
nature [1]. Among the many and varied
models of this type, we have a particular interest in systems where
elements have their own dynamics, i.e. the nodes of the network are
dynamic objects themselves.
\hspace{0.3cm}As an example, we have been studying a dynamical system model of the
immune network . In this model, each element or node is composed of
a number of B-cells and antibodies with the same idiotype (i.e. they
have the same antigen 'detector') - this subunit is called a clone.
The dynamics of a given clone is described by a pair of ordinary
differential equations.
\hspace{0.3cm}One particular feature of the immune system is that each clone
interacts with only a finite number of other clones irrespective of
the number of clones (i.e. number of idiotypes in the system), $N$.
This property allows protection against a wide range of antigen,
with antigen of a specific type only having a 'local' effect on the
entire immune network. We have derived a partial differential
equation to describe the population of B-cells and antibodies by
using the dynamical replica
theory[2]. However, this model is
rather complicated and is difficult to analyze theoretically. It is
desirable to study a model in which each element has a dynamical
nature is simple enough to be able to analyze theoretically.
\hspace{0.3cm}In this talk, as an example of such a tractable system, we discuss $N$ coupled phase oscillators as introduced by
Kuramoto[3]. In this model, each oscillator has a
definite amplitude, and the state of a given oscillator is described
by its phase $\phi \in R$. The evolution equation for phase $\phi_i$
of $i$-th oscillator is given by
\begin{eqnarray}
\frac{d}{dt} \phi_i &=& \omega _i + \sum_{j \ne i} J_{ij}\sin(\phi_j
- \phi_i) + \eta _i, \label{eq:phi}
\end{eqnarray}
where $\eta_i(t)$ is Gaussian white noise with variance $2T$.
\hspace{0.3cm}The system simplifies in the case where $\omega_i=\omega$ for any
$i$ and where $J_{ij}=J_{ji}$. Then eq. (1) can be
rewritten (in the frame of reference moving with angular velocity
$\omega$) as
\begin{eqnarray}
\frac{d}{dt} \phi_i &=& - \frac{\partial}{\partial \phi_i}
H + \eta _i,\\
H & = & - \sum_{i<j} J_{ij}\cos(\phi_i - \phi_j).
\end{eqnarray}
These assumptions allow us to investigate a Hamiltonian system.
\hspace{0.3cm}First, we focus on the following result of Ichimomiya[4]: the sparse random network with finite
connectivity behaves similarly to a fully connected model with
disordered bonds. The quenched Gaussian disordered bonds can be seen
to have a similar effect on the system to the random number of
connections in a sparse system.
\hspace{0.3cm}By restricting ourselves to this Hamiltonian subcase,
we are able to
examine Ichinomiya's result analytically in the regime of finite $c$
comparing phase diagrams and the order parameters in these
models. Further, we perform numerical simulations and compare our
theoretical and numerical results.
\hspace{0.3cm}We then tackle the more challenging dynamical relaxation behaviour
of this system. By using a maximum entropy assumption we are able
to gain some analytic control of the overall system behaviour and we
investigate the distribution of the phases as the system relaxes.\\
1) S. Dorgovtsev and J.F.F Mendes
{\em Evolution of networks: From Biological Nets to the internet and
WWW} Oxford University Press, 2003\\
2) T. Uezu, C. Kadono, J.P.L. Hatchett and A.C.C. Coolen {\em Prog. Theo. Phys. Supp.} {\bf 161}
pp. 385-388, 2006\\
3) Y. Kuramoto {\em Chemical waves,
Oscillations and Turbulence} Springer-Verlag, 1984\\
4) T. Ichinomiya {\em Phys. Rev. E} {\bf 72} 016109, 2005Fri May 04 05:48:10 CEST 2007November4350-01Laboratory for Information Globalization and Harmonization Technologies:
A New Research InitiativeWorking Paper2001Information Technologies Globalization Harmonization connectivity electronic