2,905 research outputs found
NetzCope: A Tool for Displaying and Analyzing Complex Networks
Networks are a natural and popular mechanism for the representation and
investigation of a broad class of systems. But extracting information from a
network can present significant challenges. We present NetzCope, a software
application for the display and analysis of networks. Its key features include
the visualization of networks in two or three dimensions, the organization of
vertices to reveal structural similarity, and the detection and visualization
of network communities by modularity maximization.Comment: 16 pages, Proceedings of ICQBIC2010; minor improvements to wording in
v
Expectation-driven interaction: a model based on Luhmann's contingency approach
We introduce an agent-based model of interaction, drawing on the contingency
approach from Luhmann's theory of social systems. The agent interactions are
defined by the exchange of distinct messages. Message selection is based on the
history of the interaction and developed within the confines of the problem of
double contingency. We examine interaction strategies in the light of the
message-exchange description using analytical and computational methods.Comment: 37 pages, 16 Figures, to appear in Journal of Artificial Societies
and Social Simulation
Dual-Mode Vector-Quantised Low-Rate Cordless Videophone Systems for Indoors and Outdoors Applications
Dual-mode reconfigurable wireless videophone transceivers are proposed for noise-, rather than interference-limited indoors and outdoors applications and their video quality, bit rate, robustness, and complexity issues are analyzed. A suite of fixed, but arbitrarily programmable low-rate, perceptually weighted vector quantized (VQ) codecs with and without run-length compression (RLC) are contrived for quarter common intermediate format (QCIF) videophone sequences. The 11.36-kb/s Codec 1 is BoseâChaudhuriâHochquenghem (BCH) (127,71,9) coded to a rate of 20.32 kb/s and this arrangement is comparatively studied along with the 8-kb/s Codec 2 and BCH(127,50,13) scheme, which has the same 20.32-kb/s overall rate. The source-sensitivity matched Systems 1â6 characterized in Table IV were contrived to comparatively study the range of system design options. For example, using Codec 1 in System 1 and coherent pilot symbol assisted 16-level quadrature amplitude modulation (16-PSAQAM), an overall signaling rate of 9 kBd was yielded, if the noise-limited channel had a signal-to-noise ratio (SNR) in excess of about 22 dB in the vicinity of the basestation or in indoors scenarios. In contrast, over lower quality outdoors channels near the fringes of the cell, the more robust 4-QAM mode of operation had to be invoked, which required twice as many time slots to accommodate the resulting 18-kBd stream and hence, reduced the total number of users supported. The robustness of Systems 2â4, and 6 was increased using automatic repeat requests (ARQ), again, inevitably reducing the number of users supported, which was between 6 and 16. In a bandwidth of 200 kHz, similarly to the Pan-European GSM mobile radio systemâs speech channel, using systems 1, 3, 4, or 5, for example, 16 and eight videophone users can be supported in the 16- and 4-QAM modes, respectively, while in dual-mode cells the number of users is between eight and 16. The basic system characteristics are highlighted in Table IV. Index TermsâFixed-rate video coding, QAM video communications, vector-quantized video coding, wireless video telephony
Searching for Communities in Bipartite Networks
Bipartite networks are a useful tool for representing and investigating
interaction networks. We consider methods for identifying communities in
bipartite networks. Intuitive notions of network community groups are made
explicit using Newman's modularity measure. A specialized version of the
modularity, adapted to be appropriate for bipartite networks, is presented; a
corresponding algorithm is described for identifying community groups through
maximizing this measure. The algorithm is applied to networks derived from the
EU Framework Programs on Research and Technological Development. Community
groups identified are compared using information-theoretic methods.Comment: 12 pages, 4 figures, to appear in "Proceedings of the 5th Jagna
International Workshop: Stochastic and Quantum Dynamics of Biomolecular
Systems," C. C. Bernido and M. V. Carpio-Bernido, editors. A version with
full-quality figures and larger file size is available at
http://ccm.uma.pt/publications/Barber-Faria-Streit-Strogan-2008.pd
Beyond Activation: Characterizing Microglial Functional Phenotypes
Classically, the following three morphological states of microglia have been defined: ramified, amoeboid and phagocytic. While ramified cells were long regarded as ârestingâ, amoeboid and phagocytic microglia were viewed as âactivatedâ. In aged human brains, a fourth, morphologically novel state has been described, i.e., dystrophic microglia, which are thought to be senescent cells. Since microglia are not replenished by blood-borne mononuclear cells under physiological circumstances, they seem to have an âexpiration dateâ limiting their capacity to phagocytose and support neurons. Identifying factors that drive microglial aging may thus be helpful to delay the onset of neurodegenerative diseases, such as Alzheimerâs disease (AD). Recent progress in single-cell deep sequencing methods allowed for more refined differentiation and revealed regional-, age- and sex-dependent differences of the microglial population, and a growing number of studies demonstrate various expression profiles defining microglial subpopulations. Given the heterogeneity of pathologic states in the central nervous system, the need for accurately describing microglial morphology and expression patterns becomes increasingly important. Here, we review commonly used microglial markers and their fluctuations in expression in health and disease, with a focus on IBA1 low/negative microglia, which can be found in individuals with liver disease
Einfluss von lebenden Mulchen auf die Begleitflora und die WeizenertrĂ€ge unter Bedingungen des Ăkolandbau
For the success of no-tillage in organic farming, new tools have to be developed to control weeds. One possible strategy could be sowing the main crop into an earlier established living mulch of easily controllable cover crops.
Field trials were carried out in the Swiss midlands to investigate the impact of different legume cover crops on weed populations and grain yield of directly drilled winter wheat (Triticum aestivum L.) in a living mulch system. In general, weed suppressing effect was best with highly productive legumes. A significant reduction of the weed density of dicotyle, monocotyle, and spring germinating species was observed. Though, effective weed suppression resulted also in strong competition with the winter wheat. In order to improve the practicability of such systems, seeding technique of the main crop and living mulch management should be investigated
No-Tillage in Europe - State of the Art: Constraints and Perspectives
No-tillage in Europe contains a review of developments over the last three decades beginning in the late 1960s. Reasons for attempts to introduce this soil conserving production method are outlined and obstacles affecting the uptake of no-tillage throughout Europe are identified. Updated data are provided for the uptake of both conservation tillage and no-tillage in the member countries of the European Conservation Agriculture Federation.
Further explanations for the low uptake of no-tillage and even conservation tillage when compared to other regions in the world are explored. The specificity of European conditions whether natural, human or political are used to provide arguments against the successful adoption of no-tillage in Europe.
However, increased awareness of farmers, politicians and society as a whole that soils are a non-renewable resource are leading to gradual changes in the overall approach to soil conservation. The implementation of a European Soil Framework Directive is considered to be an important step towards the recognition that conservation tillage and no-tillage is both an economical and ecological sustainable method for crop production. It is anticipated that this will promote the concept of Conservation Agriculture and increase adoption levels throughout Europe
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