Geography of Twitter Networks

Social NetworksSocial Networks, Available online 25 August 2011

Yuri Takhteyev, Anatoliy Gruzd, and Barry Wellman

“Highlights:

  • We examine the influence of distance and related variables on Twitter ties.
  • A substantial share of ties (39%) lies within the same metropolitan region.
  • For non-local ties distance, borders, and language differences affect Twitter ties.
  • The number of airline flights between the parties is the best predictor of ties.

“The paper examines the influence of geographic distance, national boundaries, language, and frequency of air travel on the formation of social ties on Twitter, a popular micro-blogging website. Based on a large sample of publicly available Twitter data, our study shows that a substantial share of ties lies within the same metropolitan region, and that between regional clusters, distance, national borders and language differences all predict Twitter ties. We find that the frequency of airline flights between the two parties is the best predictor of Twitter ties. This highlights the importance of looking at pre-existing ties between places and people.”

Remote Sensing as a Botanic Garden Tool

ArnoldiaArnoldia, Volume 69, Number 1, 2011

Ericka Witcher and Patrick Griffith

“Remote sensing is a tool already in use for plant exploration, ecology, forestry, habitat restoration, and other related fields. It also has great potential in botanic gardens for botany, horticultural science, and management purposes. At Montgomery Botanical Center, located in Coral Gables, Florida, we were able to improve our assessment of the property with the addition of new software that provided the capability for deeper evaluation of the collections and natural resources using remote sensing imagery and data. By adding LIDAR (Light Detection And Ranging) imagery to maps and employing techniques normally used at larger regional scales, new information was discovered about the garden and its collections.

First-Return LIDAR image of MBC property

First-Return LIDAR image of MBC property showing topmost surfaces, where bright yellow is the highest elevation and deep blue is the lowest. By Ericka Witcher for Montgomery Botanical Center

“Garden maps serve multiple purposes. Their primary use is as a location catalog—what a garden has and where it is. People who use the garden, whether staff or visitors, will want to know where certain features are at some point. The information displayed in this kind of map can reflect the vastly different purposes of, say, a researcher examining different subspecies of Coccothrinax miraguama (miraguama palm), an irrigation technician repairing a break, or a visitor looking for the restroom, but all three of their garden maps would need to show what things are and where they are located. On the other hand, maps can also be used for more dynamic purposes in the garden. New areas of horticultural and scientific interest can be illuminated through the addition of a spatial or geographic component—where things are in relation to something else. Spatial relationships in a botanical garden, for example, can examine how close vulnerable plants are to open spaces or high-use visitor areas, how tree canopies change over time, or the density of plantings. Expanding beyond the property, considerations regarding latitude and regional topography can be taken into account. Integrating a garden map into a Geographic Information System (GIS) is a way to keep and readily analyze a lot of data about a lot of different things in a garden.”

Globalisation and Wage Differentials: A Spatial Analysis

The Manchester SchoolThe Manchester School, Special Issue: Regional and Spatial Economics, Volume 79, Issue 5, pages 1018–1034, September 2011, Published online 25 August 2011

Bernard Fingleton and Michelle Catherine Baddeley

“Fujita, Krugman and Venables (FKV) develop a model in which international wage differentials encourage industrial mobility. We argue that globalization has another important dimension. Shocks may originate in a single country but, with modern transportation and telecommunications media, shocks spread quickly and with multiple shocks complex spillovers will be generated. We assess these forces in an analysis of international wage convergence, identifying a non-linear relationship and showing that not all countries converge. Given that the FKV model omits many of the causes of non-convergence, our evidence further demonstrates that the FKV model could usefully be extended.”