The Demise of Distance? The Declining Role of Physical Proximity for Knowledge Transmission

The transmission of knowledge diminishes with physical distance, one factor explaining the geographic clustering of scientific and industrial activity. The authors investigate how those distances have stretched over time-between collaborating inventors, and between inventors and the technology that inspires them. While physical distance is still a factor, it is clear that its constraining effects have weakened, especially for particular types of innovators, technologies, and regions of the United States. Copyright 2006 Blackwell Publishing.

Telomere dysfunction-induced foci (TIF) formation after <i>WRN</i> knockdown.

<p><b>A</b>. Representative confocal micrograph images of cells from two telomerase positive cell lines, HeLa and MCF7, and three ALT cell lines, VA-13, Saos-2 and U-2 OS. Cells were fixed 48 hours after transfection with scrambled control (SC) <i>siRNAs</i>, <i>WRN siRNAs</i> or <i>TRF2 siRNAs</i> and subjected to fluorescent <i>in situ</i> hybridization (FISH) with a Cy3-labeled telomeric PNA probe and immunofluorescently labeled with an antibody to phosphorylated histone 2A (γH2AX). As TRF2 is a member of the shelterin complex, <i>TRF2</i> knockdown was used as a positive control. The telomere is labeled with a Cy3-PNA probe in red, γH2AX in green, and the nucleus is stained with DAPI (blue). <b>B</b>. A graphical representation of at least three independent experiments were averaged to yield the percentage of each cell type with γH2AX co-localization with the telomere, indicative of telomere dysfunction induced foci (TIF). Western blots confirm the ability of <i>TRF2 siRNAs</i> to reduce TRF2 expression.</p