5,782 research outputs found
Inferring land use from mobile phone activity
Understanding the spatiotemporal distribution of people within a city is
crucial to many planning applications. Obtaining data to create required
knowledge, currently involves costly survey methods. At the same time
ubiquitous mobile sensors from personal GPS devices to mobile phones are
collecting massive amounts of data on urban systems. The locations,
communications, and activities of millions of people are recorded and stored by
new information technologies. This work utilizes novel dynamic data, generated
by mobile phone users, to measure spatiotemporal changes in population. In the
process, we identify the relationship between land use and dynamic population
over the course of a typical week. A machine learning classification algorithm
is used to identify clusters of locations with similar zoned uses and mobile
phone activity patterns. It is shown that the mobile phone data is capable of
delivering useful information on actual land use that supplements zoning
regulations.Comment: To be presented at ACM UrbComp201
Micro-CT Characterization of Human Trabecular Bone in Osteogenesis Imperfecta
Osteogenesis imperfecta (OI) is a genetic syndrome affecting collagen synthesis and assembly. Its symptoms vary widely but commonly include bone fragility, reduced stature, and bone deformity. Because of the small size and paucity of human specimens, there is a lack of biomechanical data for OI bone. Most literature has focused on histomorphometric analyses, which rely on assumptions to extrapolate 3-D properties. In this study, a micro-computed tomography (μCT) system was used to directly measure structural and mineral properties in pediatric OI bone collected during routine surgical procedures. Surface renderings suggested a poorly organized, plate-like orientation. Patients with a history of bone-augmenting drugs exhibited increased bone volume fraction (BV/TV), trabecular number (Tb.N), and connectivity density (Eu.Conn.D). The latter two parameters appeared to be related to OI severity. Structural results were consistently higher than those reported in a previous histomorphometric study, but these differences can be attributed to factors such as specimen collection site, drug therapy, and assumptions associated with histomorphometry. Mineral testing revealed strong correlations with several structural parameters, highlighting the importance of a dual approach in trabecular bone testing. This study reports some of the first quantitative μCT data of human OI bone, and it suggests compelling possibilities for the future of OI bone assessment
Coupling Human Mobility and Social Ties
Studies using massive, passively data collected from communication
technologies have revealed many ubiquitous aspects of social networks, helping
us understand and model social media, information diffusion, and organizational
dynamics. More recently, these data have come tagged with geographic
information, enabling studies of human mobility patterns and the science of
cities. We combine these two pursuits and uncover reproducible mobility
patterns amongst social contacts. First, we introduce measures of mobility
similarity and predictability and measure them for populations of users in
three large urban areas. We find individuals' visitations patterns are far more
similar to and predictable by social contacts than strangers and that these
measures are positively correlated with tie strength. Unsupervised clustering
of hourly variations in mobility similarity identifies three categories of
social ties and suggests geography is an important feature to contextualize
social relationships. We find that the composition of a user's ego network in
terms of the type of contacts they keep is correlated with mobility behavior.
Finally, we extend a popular mobility model to include movement choices based
on social contacts and compare it's ability to reproduce empirical measurements
with two additional models of mobility
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