29 research outputs found
Router-level community structure of the Internet Autonomous Systems
The Internet is composed of routing devices connected between them and
organized into independent administrative entities: the Autonomous Systems. The
existence of different types of Autonomous Systems (like large connectivity
providers, Internet Service Providers or universities) together with
geographical and economical constraints, turns the Internet into a complex
modular and hierarchical network. This organization is reflected in many
properties of the Internet topology, like its high degree of clustering and its
robustness.
In this work, we study the modular structure of the Internet router-level
graph in order to assess to what extent the Autonomous Systems satisfy some of
the known notions of community structure. We show that the modular structure of
the Internet is much richer than what can be captured by the current community
detection methods, which are severely affected by resolution limits and by the
heterogeneity of the Autonomous Systems. Here we overcome this issue by using a
multiresolution detection algorithm combined with a small sample of nodes. We
also discuss recent work on community structure in the light of our results
Resource heterogeneity and community structure: A case study in Heliconia imbricata Phytotelmata
Complex or non-additive differences in the distribution and abundance of arthropod species inhabiting the water-filled bracts of Heliconia imbricata can be created by simple manipulations of resource levels. The primary resources for these assemblages are the corollas of the flowers that accumulate in the bracts. Removing or adding corollas to individual bracts changes the pattern in the abundance of arthropod species within each bract such that bracts with different treatments ultimately differ in composition and numerical associations among species. These results suggest that direct and indirect resource-mediated factors can structure or significantly affect the distribution and abundance of species in these and perhaps other assemblages. Thus, in natural communities, if resources are heterogeneous among patches (such as among the bracts in this study) structure in a given patch may be a function of the resource level of that patch and can differ significantly from neighboring patches that provide different resource levels.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47788/1/442_2004_Article_BF00665591.pd
Rectal obstruction after a vaginal posterior compartment polypropylene mesh fixed to the sacrospinous ligaments
Item does not contain fulltextWe present a case in which a polypropylene mesh was placed over the posterior vaginal wall and was fixed to the sacrospinous ligaments on both sides. Postoperative a rectal obstruction developed which was only resolved after splitting the entire mesh in the midline. It is hypothesised that the obstruction was due to the fixation of the mesh with irresolvable suture material to the sacrospinous ligaments acting as a hinge on which the bowel folded