Interplay between function and structure in complex networks

We show that abrupt structural transitions can arise in functionally optimal networks, driven by small changes in the level of transport congestion. Our results offer an explanation as to why so many diverse species of network structure arise in Nature (e.g. fungal systems) under essentially the same environmental conditions. Our findings are based on an exactly solvable model system which mimics a variety of biological and social networks. We then extend our analysis by introducing a novel renormalization scheme involving cost motifs, to describe analytically the average shortest path across multiple-ring-and-hub networks. As a consequence, we uncover a 'skin effect' whereby the structure of the inner multi-ring core can cease to play any role in terms of determining the average shortest path across the network.Comment: Expanded version of physics/0508228 with additional new result

Assessment of RANS and DES methods for realistic automotive models

This paper presents a comprehensive investigation of RANS and DES models for the Ahmed car body and a realistic automotive vehicle; the DrivAer model. A variety of RANS models, from the 1-equation Spalart Allmaras model to a low-Reynolds number Reynolds Stress model have shown an inability to consistently correctly capture the flow field for both the Ahmed car body and DrivAer model, with the under-prediction of the turbulence in the initial separated shear layer found as a key deficiency. It has been shown that the use of a hybrid RANS-LES model (in this case, Detached Eddy Simulation) offers an advantage over RANS models in terms of the force coefficients, and general flow field for both the Ahmed car body and the DrivAer model. However, for both cases even at the finest mesh level hybrid RANS-LES methods still exhibited inaccuracies. Suggestions are made on possible improvements, in particular on the use of embedded LES with synthetic turbulence generation. Finally the computational cost of each approach is compared, which shows that whilst hybrid RANS-LES offer a clear benefit over RANS models for automotive relevant flows they do so at a much increased cost

Youth and the Millennium Development Goals (MDGs): Challenges and Opportunities for Implementation

Young people ages 15 to 24 are 1.2 billion of the world’s human capital. Around the world, many of them are already making contributions to the Millennium Development Goals (MDGs), and their work should be further acknowledged and strengthened. Increasingly, youth are recognized as key participants in decision-making and development, as reflected in the growing presence of non-governmental youth organizations and the upsurge of youth advisory boards and committees to international institutions and programmes. Yet building the capacity of and creating sustained partnerships with young people are crucial strategies to achieving the MDGs that have not been fully realized by the international community. This paper aims to provide an overview of youth participation as it currently exists, to outline the ways in which youth are directly involved and affected by each Goal, to demonstrate the ways in which young people are contributing to the MDGs, and to provide ‘Options for Action’ that governments, the United Nations system, donors and other actors can harness, support, and scale-up in order to support young people in making significant contributions to achieving the MDGs. Part I outlines the existing mechanisms for youth participation in development policy. These channels can be used by governments and institutions to strengthen and mobilize young people as partners in policy formulation. Successful modes of participation should be recognized and replicated, and also adapted to the challenging political and socio-economic realities facing many youth-led and youth-serving organizations. Part II presents youth participation as it relates directly to the MDGs. Each goal is analyzed with respect to its effect on young peoples lives as well as how young people can play – and indeed are playing — a role in its implementation. Under each goal are a number of “Options for Action” that governments, the UN and multilateral organizations can use to fully harness the contributions that youth can make to achieving the MDGs. Part III outlines the synergies between the Options for Action presented in this report and the Quick Wins proposed by the Millennium Project. The Options for Action are complimentary and provide a process to implement the Quick Win actions, using young people as key implementing agents and service providers. Part III also outlines a number of youth-focused Quick Wins that can make a significant and measurable difference to the state of young people in target countries. Part IV elaborates on how youth can participate in achieving the MDGs and contains cross-cutting recommendations on youth engagement in all 8 Goals. Overall, the report demonstrates that investing in youth will provide the longest and most effective dividend towards meeting the Millennium Development Goals (MDGs) by building the social capital needed to foster pragmatic development. Indeed, without the involvement of young people, a demographic that comprises one fifth of the world’s total population, the full achievement of the MDGs will remain elusive and their long-term sustainability will be compromised. Youth participation is currently quite varied, ranging from effective, to sometimes tokenistic, to often non-existent. There are specific ways in which youth and youth organizations can contribute to the design and implementation of MDG-based strategies, some of which are outlined in this document. Many projects are already happening, but there is much work left still to be done.Youth participation; Millennium Development Goals (MDGs); Poverty Eradication

How does Europe Make Its Mind Up? Connections, cliques, and compatibility between countries in the Eurovision Song Contest

We investigate the complex relationships between countries in the Eurovision Song Contest, by recasting past voting data in terms of a dynamical network. Despite the British tendency to feel distant from Europe, our analysis shows that the U.K. is remarkably compatible, or 'in tune', with other European countries. Equally surprising is our finding that some other core countries, most notably France, are significantly 'out of tune' with the rest of Europe. In addition, our analysis enables us to confirm a widely-held belief that there are unofficial cliques of countries -- however these cliques are not always the expected ones, nor can their existence be explained solely on the grounds of geographical proximity. The complexity in this system emerges via the group 'self-assessment' process, and in the absence of any central controller. One might therefore speculate that such complexity is representative of many real-world situations in which groups of 'agents' establish their own inter-relationships and hence ultimately decide their own fate. Possible examples include groups of individuals, societies, political groups or even governments

Stepping Responses of Young and Old Adults to Postural Disturbances: Kinematics

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111171/1/j.1532-5415.1994.tb04972.x.pd

Do Neural Factors Underlie Age Differences in Rapid Ankle Torque Development?

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111232/1/j.1532-5415.1996.tb03737.x.pd

Sporogenesis in Physcomitrium patens: Intergenerational collaboration and the development of the spore wall and aperture

Although the evolution of spores was critical to the diversification of plants on land, sporogenesis is incompletely characterized for model plants such as Physcomitrium patens. In this study, the complete process of P. patens sporogenesis is detailed from capsule expansion to mature spore formation, with emphasis on the construction of the complex spore wall and proximal aperture. Both diploid (sporophytic) and haploid (spores) cells contribute to the development and maturation of spores. During capsule expansion, the diploid cells of the capsule, including spore mother cells (SMCs), inner capsule wall layer (spore sac), and columella, contribute a locular fibrillar matrix that contains the machinery and nutrients for spore ontogeny. Nascent spores are enclosed in a second matrix that is surrounded by a thin SMC wall and suspended in the locular material. As they expand and separate, a band of exine is produced external to a thin foundation layer of tripartite lamellae. Dense globules assemble evenly throughout the locule, and these are incorporated progressively onto the spore surface to form the perine external to the exine. On the distal spore surface, the intine forms internally, while the spiny perine ornamentation is assembled. The exine is at least partially extrasporal in origin, while the perine is derived exclusively from outside the spore. Across the proximal surface of the polar spores, an aperture begins formation at the onset of spore development and consists of an expanded intine, an annulus, and a central pad with radiating fibers. This complex aperture is elastic and enables the proximal spore surface to cycle between being compressed (concave) and expanded (rounded). In addition to providing a site for water intake and germination, the elastic aperture is likely involved in desiccation tolerance. Based on the current phylogenies, the ancestral plant spore contained an aperture, exine, intine, and perine. The reductive evolution of liverwort and hornwort spores entailed the loss of perine in both groups and the aperture in liverworts. This research serves as the foundation for comparisons with other plant groups and for future studies of the developmental genetics and evolution of spores across plants

Whole-genome sequencing for national surveillance of Shiga toxin–producing Escherichia coli O157

Background. National surveillance of gastrointestinal pathogens, such as Shiga toxin–producing Escherichia coli O157 (STEC O157), is key to rapidly identifying linked cases in the distributed food network to facilitate public health interventions. In this study, we used whole-genome sequencing (WGS) as a tool to inform national surveillance of STEC O157 in terms of identifying linked cases and clusters and guiding epidemiological investigation. Methods. We retrospectively analyzed 334 isolates randomly sampled from 1002 strains of STEC O157 received by the Gastrointestinal Bacteria Reference Unit at Public Health England, Colindale, in 2012. The genetic distance between each isolate, as estimated by WGS, was calculated and phylogenetic methods were used to place strains in an evolutionary context. Results. Estimates of linked clusters representing STEC O157 outbreaks in England and Wales increased by 2-fold when WGS was used instead of traditional typing techniques. The previously unidentified clusters were often widely geographically distributed and small in size. Phylogenetic analysis facilitated identification of temporally distinct cases sharing common exposures and delineating those that shared epidemiological and temporal links. Comparison with multi locus variable number tandem repeat analysis (MLVA) showed that although MLVA is as sensitive as WGS, WGS provides a more timely resolution to outbreak clustering. Conclusions. WGS has come of age as a molecular typing tool to inform national surveillance of STEC O157; it can be used in real time to provide the highest strain-level resolution for outbreak investigation. WGS allows linked cases to be identified with unprecedented specificity and sensitivity that will facilitate targeted and appropriate public health investigations