Antecedents of Growth in Network Competition: Quality or Quantity?

This research examines the impact of two potential antecedents of growth in high-technology, network industries. The first antecedent, installed base, is traditionally framed as a key driver of growth in these settings. The second, product quality, is thought to have only random influences on growth. This work tests the influence of both of these variables on growth in the packaged application software industry, and proposes that their relative influence may be contingent upon the network intensity of a given market or segment. In turn, installed base and timing of product release are proposed to have a significant impact on quality. The sample for this study encompassed five segments of the packaged application software industry from 1986-1998, including word processing, spreadsheets, desktop publishing, CAD, and personal finance. Several results from the empirical analysis offer useful insights into the nature of network industries, and implications for strategic management in these domains. First, installed base size exhibits a negative relationship with growth that becomes more positive as size increases. Second, product quality is positively and significantly associated with installed base growth. Third, the impact of size on growth is shown to vary across industry segments, suggesting that the influence of network effects may not be as homogeneous as extant theory implies. Finally, installed base is associated with higher baseline product quality within periods, consistent with the notion that a large installed base confers learning-based advantages to quality. Together, these findings indicate that competitive dynamics in network industries may be more complex than previously thought. This research extends existing theoretical and empirical work on network effects and positive feedback, and suggests new avenues for effective strategies in emerging high-technology settings

Prioritizing ecological restoration among sites in multi‐stressor landscapes

Most ecosystems are impacted by multiple local and long‐distance stressors, many of which interact in complex ways. We present a framework for prioritizing ecological restoration efforts among sites in multi‐stressor landscapes. Using a simple model, we show that both the economic and sociopolitical costs of restoration will typically be lower at sites with a relatively small number of severe problems than at sites with numerous lesser problems. Based on these results, we propose using cumulative stress and evenness of stressor impact as complementary indices that together reflect key challenges of restoring a site to improved condition. To illustrate this approach, we analyze stressor evenness across the world’s rivers and the Laurentian Great Lakes. This exploration reveals that evenness and cumulative stress are decoupled, enabling selection of sites where remediating a modest number of high‐intensity stressors could substantially reduce cumulative stress. Just as species richness and species evenness are fundamental axes of biological diversity, we argue that cumulative stress and stressor evenness constitute fundamental axes for identifying restoration opportunities in multi‐stressor landscapes. Our results highlight opportunities to boost restoration efficiency through strategic use of multi‐stressor datasets to identify sites that maximize ecological response per stressor remediated. This prioritization framework can also be expanded to account for the feasibility of remediation and the expected societal benefits of restoration projects.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134184/1/eap1346_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134184/2/eap1346.pd

A high-throughput in vivo micronucleus assay for genome instability screening in mice.

We describe a sensitive, robust, high-throughput method for quantifying the formation of micronuclei, markers of genome instability, in mouse erythrocytes. Micronuclei are whole chromosomes or chromosome segments that have been separated from the nucleus. Other methods of detection rely on labor-intensive, microscopy-based techniques. Here we describe a 2-d, 96-well plate-based flow cytometric method of micronucleus scoring that is simple enough for a research technician experienced in flow cytometry to perform. The assay detects low levels of genome instability that cannot be readily identified by classic phenotyping, using 25 μl of blood. By using this assay, we have screened >10,000 blood samples and discovered novel genes that contribute to vertebrate genome maintenance, as well as novel disease models and mechanisms of genome instability disorders. We discuss experimental design considerations, including statistical power calculation, we provide troubleshooting tips and we discuss factors that contribute to a false-positive increase in the number of micronucleated red blood cells and to experimental variability.Acknowledgments We thank M. Hitcham and N. Harman for assistance with blood collections, W. Cheng for assistance with flow cytometry during high-throughput screening and K. Dry for comments on the manuscript. R.E.M. is supported by Cancer Research UK (CRUK; project grant C20510/A12401). D.J.A. is supported by CRUK. D.J.A. and B.L.N. are supported by the Wellcome Trust. Research in the Jackson Laboratory is funded by CRUK program grant no. C6/A11224, the European Research Council and the European Community Seventh Framework Programme grant agreement no. HEALTH-F2-2010-259893 (DDResponse). Core funding is provided by CRUK (C6946/A14492) and the Wellcome Trust (WT092096). S.P.J. receives his salary from the University of Cambridge, UK, supplemented by CRUK. G.B. is funded by CRUK program grant no. C6/A11224.This is the accepted manuscript for a paper published in Nature Protocols 10, 205–215 (2015) doi:10.1038/nprot.2015.010, Published online 31 December 201

Oersted Lecture 2014: Physics education research and teaching modern Modern Physics

Citation: Zollman, D. (2016). Oersted Lecture 2014: Physics education research and teaching modern Modern Physics. American Journal of Physics, 84(8), 573-580. doi:10.1119/1.4953824Modern Physics has been used as a label for most of physics that was developed since the discovery of X-rays in 1895. Yet, we are teaching students who would not use the label "modern" for anything that happened before about 1995, when they were born. So, are we and our students in worlds that differ by a century? In addition to content, sometimes our students and we have differing views about methods and styles of teaching. A modern course in any topic of physics should include applications of contemporary research in physics education and the learning sciences as well as research and developments in methods of delivering the content. Thus, when we consider teaching Modern Physics, we are challenged with deciding what the content should be, how to adjust for the ever increasing information on how students learn physics, and the constantly changing tools that are available to us for teaching and learning. When we mix all of these together, we can teach modern Modern Physics or maybe teach Modern Physics modernly. © 2016 American Association of Physics Teachers

Influence of age on respiratory modulation of muscle sympathetic nerve activity, blood pressure and baroreflex function in humans

New Findings What is the central question of this study? Does ageing influence the respiratory‐related bursting of muscle sympathetic nerve activity (MSNA) and the association between the rhythmic fluctuations in MSNA and blood pressure (Traube–Hering waves) that occur with respiration? What is the main finding and its importance? Despite the age‐related elevation in MSNA, the cyclical inhibition of MSNA during respiration is similar between young and older individuals. Furthermore, central respiratory–sympathetic coupling plays a role in the generation of Traube–Hering waves in both young and older humans. Healthy ageing and alterations in respiratory–sympathetic coupling have been independently linked with heightened sympathetic neural vasoconstrictor activity. We investigated how age influences the respiratory‐related modulation of muscle sympathetic nerve activity (MSNA) and the association between the rhythmic fluctuations in MSNA and blood pressure that occur with respiration (Traube–Hering waves; THW). Ten young (22 ± 2 years; mean ± SD) and 10 older healthy men (58 ± 6 years) were studied while resting supine and breathing spontaneously. MSNA, blood pressure and respiration were recorded simultaneously. Resting values were ascertained and respiratory cycle‐triggered averaging of MSNA and blood pressure measurements performed. The MSNA burst incidence was higher in older individuals [22.7 ± 9.2 versus 42.2 ± 13.7 bursts (100 heart beats)−1, P < 0.05], and was reduced to a similar extent in the inspiratory to postinspiratory period in young and older subjects (by ∼25% compared with mid‐ to late expiration). A similar attenuation of MSNA burst frequency (in bursts per minute), amplitude and total activity (burst frequency × mean burst amplitude) was also observed in the inspiratory to postinspiratory period in both groups. A significant positive correlation between respiratory‐related MSNA and the magnitude of Traube–Hering waves was observed in all young (100%) and most older subjects (80%). These data suggest that the strength of the cyclical inhibition of MSNA during respiration is similar between young and older individuals; thus, alterations in respiratory–sympathetic coupling appear not to contribute to the age‐related elevation in MSNA. Furthermore, central respiratory–sympathetic coupling plays a role in the generation of Traube–Hering waves in both healthy young and older humans