53,628 research outputs found
Citing for High Impact
The question of citation behavior has always intrigued scientists from
various disciplines. While general citation patterns have been widely studied
in the literature we develop the notion of citation projection graphs by
investigating the citations among the publications that a given paper cites. We
investigate how patterns of citations vary between various scientific
disciplines and how such patterns reflect the scientific impact of the paper.
We find that idiosyncratic citation patterns are characteristic for low impact
papers; while narrow, discipline-focused citation patterns are common for
medium impact papers. Our results show that crossing-community, or bridging
citation patters are high risk and high reward since such patterns are
characteristic for both low and high impact papers. Last, we observe that
recently citation networks are trending toward more bridging and
interdisciplinary forms.Comment: 10 pages, 6 figures, 1 tabl
Robustness: a New Form of Heredity Motivated by Dynamic Networks
We investigate a special case of hereditary property in graphs, referred to
as {\em robustness}. A property (or structure) is called robust in a graph
if it is inherited by all the connected spanning subgraphs of . We motivate
this definition using two different settings of dynamic networks. The first
corresponds to networks of low dynamicity, where some links may be permanently
removed so long as the network remains connected. The second corresponds to
highly-dynamic networks, where communication links appear and disappear
arbitrarily often, subject only to the requirement that the entities are
temporally connected in a recurrent fashion ({\it i.e.} they can always reach
each other through temporal paths). Each context induces a different
interpretation of the notion of robustness.
We start by motivating the definition and discussing the two interpretations,
after what we consider the notion independently from its interpretation, taking
as our focus the robustness of {\em maximal independent sets} (MIS). A graph
may or may not admit a robust MIS. We characterize the set of graphs \forallMIS
in which {\em all} MISs are robust. Then, we turn our attention to the graphs
that {\em admit} a robust MIS (\existsMIS). This class has a more complex
structure; we give a partial characterization in terms of elementary graph
properties, then a complete characterization by means of a (polynomial time)
decision algorithm that accepts if and only if a robust MIS exists. This
algorithm can be adapted to construct such a solution if one exists
Random Network Behaviour of Protein Structures
Geometric and structural constraints greatly restrict the selection of folds
adapted by protein backbones, and yet, folded proteins show an astounding
diversity in functionality. For structure to have any bearing on function, it
is thus imperative that, apart from the protein backbone, other tunable degrees
of freedom be accountable. Here, we focus on side-chain interactions, which
non-covalently link amino acids in folded proteins to form a network structure.
At a coarse-grained level, we show that the network conforms remarkably well to
realizations of random graphs and displays associated percolation behavior.
Thus, within the rigid framework of the protein backbone that restricts the
structure space, the side-chain interactions exhibit an element of randomness,
which account for the functional flexibility and diversity shown by proteins.
However, at a finer level, the network exhibits deviations from these random
graphs which, as we demonstrate for a few specific examples, reflect the
intrinsic uniqueness in the structure and stability, and perhaps specificity in
the functioning of biological proteins.Comment: Expanded version available in Molecular BioSystem
Handling Handles: Nonplanar Integrability in Supersymmetric Yang-Mills Theory
We propose an integrability setup for the computation of correlation
functions of gauge-invariant operators in supersymmetric
Yang-Mills theory at higher orders in the large genus expansion
and at any order in the 't Hooft coupling . In
this multi-step proposal, one polygonizes the string worldsheet in all possible
ways, hexagonalizes all resulting polygons, and sprinkles mirror particles over
all hexagon junctions to obtain the full correlator. We test our
integrability-based conjecture against a non-planar four-point correlator of
large half-BPS operators at one and two loops.Comment: 6 pages, 4 figures; v2: updated references, typos, minor improvements
(published version
Multi-Paradigm Reasoning for Access to Heterogeneous GIS
Accessing and querying geographical data in a uniform way has become easier in recent years. Emerging standards like WFS turn
the web into a geospatial web services enabled place. Mediation
architectures like VirGIS overcome syntactical and semantical heterogeneity
between several distributed sources. On mobile devices,
however, this kind of solution is not suitable, due to limitations,
mostly regarding bandwidth, computation power, and available storage
space. The aim of this paper is to present a solution for providing
powerful reasoning mechanisms accessible from mobile applications
and involving data from several heterogeneous sources.
By adapting contents to time and location, mobile web information
systems can not only increase the value and suitability of the
service itself, but can substantially reduce the amount of data delivered
to users. Because many problems pertain to infrastructures
and transportation in general and to way finding in particular, one
cornerstone of the architecture is higher level reasoning on graph
networks with the Multi-Paradigm Location Language MPLL. A
mediation architecture is used as a âgraph providerâ in order to
transfer the load of computation to the best suited component â
graph construction and transformation for example being heavy on
resources. Reasoning in general can be conducted either near the
âsourceâ or near the end user, depending on the specific use case.
The concepts underlying the proposal described in this paper are
illustrated by a typical and concrete scenario for web applications
Competition and cooperation:aspects of dynamics in sandpiles
In this article, we review some of our approaches to granular dynamics, now
well known to consist of both fast and slow relaxational processes. In the
first case, grains typically compete with each other, while in the second, they
cooperate. A typical result of {\it cooperation} is the formation of stable
bridges, signatures of spatiotemporal inhomogeneities; we review their
geometrical characteristics and compare theoretical results with those of
independent simulations. {\it Cooperative} excitations due to local density
fluctuations are also responsible for relaxation at the angle of repose; the
{\it competition} between these fluctuations and external driving forces, can,
on the other hand, result in a (rare) collapse of the sandpile to the
horizontal. Both these features are present in a theory reviewed here. An arena
where the effects of cooperation versus competition are felt most keenly is
granular compaction; we review here a random graph model, where three-spin
interactions are used to model compaction under tapping. The compaction curve
shows distinct regions where 'fast' and 'slow' dynamics apply, separated by
what we have called the {\it single-particle relaxation threshold}. In the
final section of this paper, we explore the effect of shape -- jagged vs.
regular -- on the compaction of packings near their jamming limit. One of our
major results is an entropic landscape that, while microscopically rough,
manifests {\it Edwards' flatness} at a macroscopic level. Another major result
is that of surface intermittency under low-intensity shaking.Comment: 36 pages, 23 figures, minor correction
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