MCMC Sampling of Directed Flag Complexes with Fixed Undirected Graphs

Constructing null models to test the significance of extracted information is a crucial step in data analysis. In this work, we provide a uniformly sampleable null model of directed graphs with the same (or similar) number of simplices in the flag complex, with the restriction of retaining the underlying undirected graph. We describe an MCMC-based algorithm to sample from this null model and statistically investigate the mixing behaviour. This is paired with a high-performance, Rust-based, publicly available implementation. The motivation comes from topological data analysis of connectomes in neuroscience. In particular, we answer the fundamental question: are the high Betti numbers observed in the investigated graphs evidence of an interesting topology, or are they merely a byproduct of the high numbers of simplices? Indeed, by applying our new tool on the connectome of C. Elegans and parts of the statistical reconstructions of the Blue Brain Project, we find that the Betti numbers observed are considerable statistical outliers with respect to this new null model. We thus, for the first time, statistically confirm that topological data analysis in microscale connectome research is extracting statistically meaningful information

Editorial

For the first time in history, more Chinese people now live in towns and cities than in rural villages. Reaching 51% in 2011, urbanisation in China is accelerating. Convinced that this holds the key to the country’s ongoing social and economic development, China’s leaders recently announced an urbanisation target of 70% (approximately 900 million people) by 2025. However, leaders including Premier Li Keqiang have emphasised that future urbanisation would be characterised not by an expansion of megacities (dushihua 都市花), but by growth in rural towns and small cities (chengzhenhua 城镇化). The Party is essentially seeking to take the cities to the rural populace rather than bring the rural populace to the cities. Following the policy announcement at the 18th Party Congress in November 2012, a group of national ministries has been tasked with developing guidelines for promoting the urbanisation of rural China. In reality, this understudied dimension of China’s urbanisation has been underway for some time. Following the industrialisation of many rural areas along the coast and within distance of cities, many “villages” have grown to accommodate 30,000 or more workers. Today many of these villages, especially in the Pearl River Delta, have become urban-like nodes in an everwidening urban sprawl. Even in China’s agricultural heartland, vast numbers of county towns are becoming small cities, a process accelerated by the increasing concentration of public services in county towns and the expansion of industry in China’s inland provinces. In a separate thrust, in much of China, under the auspices of the Building a New Socialist Countryside programme (jianshe shehui zhuyi xin nongcun 建设社会主义新农村) that began in 2006, (1) government policies are encouraging whole villages to demolish their current housing and to move into communities of high-density townhouses, sometimes merging several villages in order to provide supermarkets, libraries, etc., in a replication of urban life. All of these forms of onrushing urbanisation are reshaping rural China – its landscape, culture, and social structures

The Guangdong Model of Urbanisation

In some parts of China – and especially in Guangdong Province in southern China – rural communities have retained ownership of much of their land when its use is converted into urban neighbourhoods or industrial zones. In these areas, the rural collectives, rather than disappearing, have converted themselves into property companies and have been re-energised and strengthened as rental income pours into their coffers. The native residents, rather than being relocated, usually remain in the village’s old residential area. As beneficiaries of the profits generated by their village collective, they have become a new propertied class, often living in middle-class comfort on their dividends and rents. How this operates – and the major economic and social ramifications – is examined through onsite research in four communities: an industrialised village in the Pearl River delta; an urban neighbourhood in Shenzhen with its own subway station, whose land is still owned and administered by rural collectives; and two villages-in-the-city in Guangzhou’s new downtown districts, where fancy housing estates and high-rise office blocks owned by village collectives are springing up alongside newly rebuilt village temples and lineage halls

Egalitarian Redistributions of Agricultural Land in China through Community Consensus: Findings from Two Surveys

Most of China's rural communities have engaged in periodic reallocations of fields in order to re-equalize household landholdings on a per capita basis, despite a national law that prohibits this. The practice of re-equalizing landholdings tells us much

SEUSS: rapid serverless deployment using environment snapshots

Modern FaaS systems perform well in the case of repeat executions when function working sets stay small. However, these platforms are less effective when applied to more complex, large-scale and dynamic workloads. In this paper, we introduce SEUSS (serverless execution via unikernel snapshot stacks), a new system-level approach for rapidly deploying serverless functions. Through our approach, we demonstrate orders of magnitude improvements in function start times and cacheability, which improves common re-execution paths while also unlocking previously-unsupported large-scale bursty workloads.Published versio

The cultural revolution warfare at Beijing's Universities

Too little research has been conducted about the fascinating, confusing upheavals that shook China during the Great Proletarian Cultural Revolution of 1966–68. Now, four decades after the mass fighting was suppressed, Andrew Walder helps to fill important gaps in our knowledge, in a 400-page book that examines the origins and chronicles the factional fighting at Beijing’s universitie

Le modèle d’urbanisation du Guangdong

Dans certaines parties de la Chine, et particulièrement au sud, dans la province du Guangdong, les communautés rurales ont conservé la propriété de la plupart de leurs terres après que leur usage a été converti en quartiers urbains ou zones industrielles. Dans ces zones, les comités villageois n’ont pas complètement disparu mais se sont transformés en sociétés collectives de gestion foncière, se renforçant grâce aux revenus locatifs ainsi générés. Au lieu d’être relogés, les résidents d’origine demeurent généralement dans l’ancienne zone résidentielle du village. Bénéficiant des revenus engendrés par leur société de gestion foncière, ils sont devenus une nouvelle classe de propriétaires vivant de dividendes et de loyers, et se sont hissés au niveau de confort de la classe moyenne. Nous avons analysé le fonctionnement de ce système ainsi que ses principales ramifications économiques et sociales dans le cadre d’une recherche de terrain menée dans quatre communautés : un village industriel dans le delta de la rivière des Perles, un quartier urbain de Shenzhen possédant sa propre station de métro et dont le terrain est toujours détenu et administré collectivement par les anciens villageois, et deux « villages-dans-la-ville » situés dans les nouveaux districts centraux de Canton où des lotissements chics et des tours de bureaux appartenant aux sociétés de gestion foncière poussent aux côtés de temples de villages et de temples lignagers récemment reconstruits

The Guangdong Model of Urbanisation

In some parts of China – and especially in Guangdong Province in southern China – rural communities have retained ownership of much of their land when its use is converted into urban neighbourhoods or industrial zones. In these areas, the rural collectives, rather than disappearing, have converted themselves into property companies and have been re-energised and strengthened as rental income pours into their coffers. The native residents, rather than being relocated, usually remain in the village’s old residential area. As beneficiaries of the profits generated by their village collective, they have become a new propertied class, often living in middle-class comfort on their dividends and rents. How this operates – and the major economic and social ramifications – is examined through onsite research in four communities: an industrialised village in the Pearl River delta; an urban neighbourhood in Shenzhen with its own subway station, whose land is still owned and administered by rural collectives; and two villages-in-the-city in Guangzhou’s new downtown districts, where fancy housing estates and high-rise office blocks owned by village collectives are springing up alongside newly rebuilt village temples and lineage halls