Community detection in networks: Structural communities versus ground truth

Algorithms to find communities in networks rely just on structural information and search for cohesive subsets of nodes. On the other hand, most scholars implicitly or explicitly assume that structural communities represent groups of nodes with similar (non-topological) properties or functions. This hypothesis could not be verified, so far, because of the lack of network datasets with information on the classification of the nodes. We show that traditional community detection methods fail to find the metadata groups in many large networks. Our results show that there is a marked separation between structural communities and metadata groups, in line with recent findings. That means that either our current modeling of community structure has to be substantially modified, or that metadata groups may not be recoverable from topology alone.Comment: 21 pages, 19 figure

How Akron Affects the Water Quality of the Cuyahoga River

The purpose of this study was to analyze whether the city of Akron had negative effects on the Cuyahoga river, and determine if the Cuyahoga River was naturally able to remediate these effects downstream. The pollutants measured in this study include hardness, bromine, residual chlorine, iron, copper, lead, nitrate, nitrite, ammonium chloride, total chlorine, fluoride, carbonate, pH, total alkalinity and cyanuric acid. This study was done using water testing strips (JNW Direct) to test the water at four different locations along the Cuyahoga River downstream (North) of Akron. This study found that the city of Akron does have a negative effect on the level of pollutants within the Cuyahoga River. This study found five pollutants measured to either be at or above an acceptable level. The results of this study indicate that the Cuyahoga River is negatively impacted by the contaminants of the urban areas surrounding it, specifically Akron, Ohio. It also indicates that the river does not succeed in remediating these pollutants by itself as it flows towards Lake Erie