From the physics of interacting polymers to optimizing routes on the London Underground

Optimizing paths on networks is crucial for many applications, ranging from subway traffic to Internet communication. Because global path optimization that takes account of all path choices simultaneously is computationally hard, most existing routing algorithms optimize paths individually, thus providing suboptimal solutions. We use the physics of interacting polymers and disordered systems to analyze macroscopic properties of generic path optimization problems and derive a simple, principled, generic, and distributed routing algorithm capable of considering all individual path choices simultaneously. We demonstrate the efficacy of the algorithm by applying it to: (i) random graphs resembling Internet overlay networks, (ii) travel on the London Underground network based on Oyster card data, and (iii ) the global airport network. Analytically derived macroscopic properties give rise to insightful new routing phenomena, including phase transitions and scaling laws, that facilitate better understanding of the appropriate operational regimes and their limitations, which are difficult to obtain otherwise.

LETs and NESTs:voices, views and vignettes

This book is a collection of essays written by teachers and academics working and researching in contexts where Native English-Speaking Teachers (NESTs) are employed and work on a daily basis with Local English Teachers (LETs).

Effect of leaf-cutting ant nests on plant growth in an oligotrophic Amazon rain forest

This study examined whether high nutrient concentrations associated with leaf-cutting ant nests influence plant growth and plant water relations in Amazon rain forests. Three nests of Atta cephalotes were selected along with 31 Amaioua guianensis and Protium sp. trees that were grouped into trees near and distant (>10 m) from nests. A 15N leaf-labelling experiment confirmed that trees located near nests accessed nutrients from nests. Trees near nests exhibited higher relative growth rates (based on stem diameter increases) on average compared with trees further away; however this was significant for A. guianensis (near nest 0.224 y−1 and far from nest 0.036 y−1) but not so for Protium sp. (0.146 y−1 and 0.114 y−1 respectively). Water relations were similarly species-specific; for A. guianensis, near-nest individuals showed significantly higher sap flow rates (16 vs. 5 cm h−1), higher predawn/midday water potentials (−0.66 vs. −0.98 MPa) and lower foliar δ13C than trees further away indicating greater water uptake in proximity to the nests while the Protium sp. showed no significant difference except for carbon isotopes. This study thus shows that plant response to high nutrient concentrations in an oligotrophic ecosystem varies with species. Lower seedling abundance and species richness on nests as compared with further away suggests that while adult plants access subterranean nutrient pools, the nest surfaces themselves do not encourage plant establishment and growth.

Tatyana Mamonova holding her underground unpublished book on Russian Women and feminism

General note: Title and date provided by Bettye Lane.

Risk from cattle trampling to nests of an endangered passerine evaluated using artificial nest experiments and simulations

Grasslands are often grazed by cattle and many grassland birds nest on the ground, potentially exposing nests to trampling. We tested for trampling risk introduced by cattle to nests of endangered Florida Grasshopper Sparrows (Ammodramus savannarum floridanus) using experimentally paired grids of artificial nests (i.e., clay targets) similar in size to nests of Florida Grasshopper Sparrows and counted the number of clay targets that were broken in paired grazed and ungrazed enclosures. Clay targets in grazed grids were trampled 3.9% more often than their respective ungrazed grids, and measurements of cattle presence or density were correlated with the number of broken clay targets, suggesting that excluding cattle during breeding is an important management recommendation for the Florida Grasshopper Sparrow. Trampling rates within grazed enclosures were spatially homogeneous with respect to cattle infrastructure such as supplemental feeding troughs and fences, and forests and stocking density were poor predictors of trampling rates when excluding ungrazed grids. We used population viability analysis to compare quasi-extinction rates, intrinsic growth rates, and median abundance in grazed and ungrazed Florida Grasshopper Sparrow aggregations to further understand the biological significance of management aimed at reducing trampling rates during the breeding season. Simulations indicated that trampling from grazing increased quasi-extinction rates by 41% while reducing intrinsic growth rates by 0.048, and reducing median abundance by an average of 214 singing males after 50 years. Management should avoid grazing enclosures occupied by Florida Grasshopper Sparrows during the nesting season to minimize trampling rates. Our methods that combine trampling experiments with population viability analysis provide a framework for testing effects from trampling on other grassland ground-nesting birds, and can directly inform conservation and management of the Florida Grasshopper Sparrow.

Evaluation of a ToF Camera for Remote Surveying of Underground Cavities Excavated by Jet Boring

Cigar Lake is a high-grade uranium deposit, located in northern Saskatchewan, Canada. In order to extract the uranium ore remotely, thus ensuring minimal radiation dose to workers and also to access the ore from stable ground, the Jet Boring System (JBS) was developed by Cameco Corporation. This system uses a high-powered water jet to remotely excavate cavities. Survey data is required to determine the final shape, volume, and location of the cavity for mine planning purposes and construction. This paper provides an overview of the challenges involved in remotely surveying a JBS-mined cavity and studies the potential use of a time-of-flight (ToF) camera for remote cavity surveying. It reports on data collected and analyzed from inside an experimental environment as well as on real data acquired on site from the Cigar Lake and Rabbit Lake mines.

From Underground to Elite: Egyptian Bloggers before and after the 2011 Uprising

This research looks at how the shift in the status of Egyptian bloggers from underground dissident voices to mainstream political and media players affected the plurality they add to the public space for discourse in Egypt’s authoritarian settings. The role of the internet – and more recently social media and bloggers – in democratic transition has been studied by various media scholars since the introduction of the worldwide web and especially after the Egyptian and Tunisian uprisings of 2011. But no work has been done to study how bringing those once-underground bloggers into the public and media spotlight affected the nature of the blogosphere and the bloggers themselves. Star bloggers were not only covered by the media after January 25th, 2011, they also started joining the media as column writers; a move that had various effects on them and the blogosphere but was never examined in media studies. The plurality the blogosphere adds to the Egyptian public space for discourse in light of those changes as well as in light of the financial and practical sustainability of blogging was hence never looked at in a context similar to Egypt’s. Guided by modified theories of the public sphere and theories of hegemony and manufacturing consent, I look at whether bloggers have been co-opted into the historical bloc in the process of renewing the social order and how this affects them and the online sphere. Also, guided by theories of power and media elites, I look at bloggers’ backgrounds to assess whether they come from power elites and are transforming into media elites, thus limiting the plurality of the online sphere. Finally, guided by theoretical works on institutionalizing and commercializing the internet, I look at how those shifts into mainstream affect the independence and freedom of the blogs and microblogs. The research uses a comparative study to assess how those changes affect prominent versus less prominent bloggers and compare their backgrounds. The study uses quantitative content analysis and framing analysis of chosen media outlets and interviews with bloggers, marketeers and media professionals. The findings trace an increase in media coverage of bloggers post January 25th, 2011, especially in the prominent bloggers category, and an overall positive framing of bloggers post the uprising. This led to the mainstreaming of bloggers into the media as well as public work, which had various implications on the freedom they had over their content and voice, both online and offline. It also points to a dramatic decrease in bloggers’ activity on their blogs in favour of mainstream and social media and due to star bloggers becoming more career-oriented and their failure to make blogs financially sustainable. The findings also indicate that more prominent bloggers seem to come from more elite backgrounds than others and enjoy luxuries that allow them the time, technology and security to post online. This research concludes that the shifts in bloggers’ status post-January 25th have limited the plurality they add to the discourse in Egypt.

Causes of extreme variability of nest density among close and similar beaches of Boavista island (Cape Verde): From 1 to 2000 annual nests per km.

[EN] The 70 km of white sandy beaches of Boa Vista island in Cape Verde harbours one of the largest rookeries of the endangered loggerhead sea turtle, Caretta caretta. From middle June to early October, approximately 2000 to 4000 females lay up to 20000 nests annually. However, female beach selection, nesting success and nest density strongly varies among beaches and spatial patterns of nest abundance and distribution are relatively constant among seasons. The numbers of nesting activities and nests have been recorded along all beaches of the island during four nesting seasons (2007-2010)

High plasticity of loggerhead nesting site fidelity: from using repeatedly the same small beach during different seasons to deposit consecutive nests in different islands distant more than 100 km

[EN] Sea turtles exhibit a strong natal homing associated with a high nesting site philopatry. Mark-recapture and genetic studies confirm these patterns suggesting differences among and within species. In the present study, we have analysed the degree of nest site fidelity of a loggerhead population nesting on the islands of Cape Verde and have evaluated the existence of intrapopulational variability in this trait. The loggerhead is the only sea turtle species that nests in Cape Verde, and 15,000–25,000 nests per season have been estimated for the whole archipelago.